Circumcision and HIV - the
Randomised Controlled Trials
'Circumcision Vindicated At
Last!' ? - hardly
The American mind seems extremely vulnerable to
the belief that any alleged knowledge which can be expressed in figures
is in fact as final and exact as the figures in which it is expressed.
- Richard Hofstadter, Anti-Intellectualism
in American Life,
quoted by Charles Seife in Proofiness
After centuries of circumcision searching for a disease
to cure, and the emergence of a new one that is sexually transmitted,
it may be that a link has actually, finally been
found. This still falls very far short of justifying Routine Infant
Circumcision, however, despite the headline of a Toronto columnist
trumpetting "Circumcision Vindicated At Last!"
studies are the most careful so far to avoid the mistakes of their predecessors:
Institute of Allergy and
Infectious Diseases (NIAID)
EMBARGOED FOR RELEASE
Wednesday, December 13, 2006
12:00 Noon ET
Circumcision Significantly Reduces Risk of Acquiring HIV
miracle! No hint of the many caveats to follow.]
Trials in Kenya and Uganda Stopped Early
The National Institute of Allergy and Infectious
Diseases (NIAID), part of the National Institutes of Health (NIH),
announced an early end to two clinical trials of adult male
circumcision because an interim review of trial data revealed that
medically performed circumcision significantly reduces a man's risk of
acquiring HIV through heterosexual intercourse. The trial in Kisumu,
Kenya, of 2,784 HIV-negative men showed a 53 percent reduction of HIV
acquisition in circumcised men relative to uncircumcised men, while a
trial of 4,996 HIV-negative men in Rakai, Uganda, showed that HIV
acquisition was reduced by 48 percent in circumcised men. ["Impressive sounding reductions in
relative risk can mask much smaller reductions in absolute risk." - editorial
in the British Medical Journal, January 19, 2008. In fact
they are inevitably greater, but their actual utility depends on the
"These findings are of great interest to public
health policy makers who are developing and implementing comprehensive
HIV prevention programs,"says NIH Director Elias A. Zerhouni, M.D.
"Male circumcision performed safely in a medical environment
complements other HIV prevention strategies and could lessen the burden
of HIV/AIDS, especially in countries in sub-Saharan Africa where,
according to the 2006 estimates from UNAIDS, 2.8 million new infections
occurred in a single year."
"Many studies have suggested that male
circumcision plays a role in protecting against HIV acquisition," notes
NIAID Director Anthony S. Fauci, M.D. "We now have confirmation — from
large, carefully controlled, randomized clinical trials [the randomisation was only in the
assignment of the paid volunteers to experimental or control groups;
they were not a random sample of the population. The trials were not -
by the nature of circumcision, could not be - double blinded or placebo
controlled, the gold standard of clinical trials.]
— showing definitively that medically performed circumcision can
significantly lower the risk of adult males contracting HIV through
heterosexual intercourse. While the initial benefit will be fewer HIV
infections in men, ultimately adult male circumcision could lead to
fewer infections in women in those areas of the world where HIV is
spread primarily through heterosexual intercourse."
The findings from the African studies may have
less impact on the epidemic in the United States for several reasons.
In the United States, most men have been circumcised. Also, there is a
lower prevalence of HIV. Moreover, most infections among men in the
United States are in men who have sex with men, for whom the amount of
benefit [if any]
provided by circumcision is unknown [but
is likely to be much less, because HIV is known to be more readily
transmitted to the receptive male partner].
Nonetheless, the overall findings of the African studies are likely to
be broadly relevant regardless of geographic location: a man at sexual
risk who is uncircumcised is more likely than a man who is circumcised
to become infected with HIV. Still, circumcision is only part of a
broader HIV prevention strategy that includes limiting the number of
sexual partners and using condoms during intercourse. [In that case, any benefit provided
by circumcision would only apply in the rare cases where a condom
breaks or comes off.]
The co-principal investigators of the Kenyan trial
are Robert Bailey, Ph.D., M.P.H., of the University of Illinois at
Chicago, and Stephen Moses, M.D., M.P.H., University of Manitoba,
Canada. In addition to NIAID support, the Kenyan trial was funded by
the Canadian Institutes of Health Research and included Kenyan
researchers Jeckoniah Ndinya-Achola, M.B.Ch.B., and Kawango Agot,
Ph.D., M.P.H. The Ugandan trial is led by Ronald Gray, M.B.B.S., M.Sc.,
of Johns Hopkins Bloomberg School of Public Health, Baltimore,
Maryland. Additional collaborators in the Ugandan trial were David
Serwadda, M.Med., M.Sc., M.P.H., Nelson Sewankambo, M.B.Ch.B.,
M.Med.M.Sc., Stephen Watya, M.B.Ch.B., M.Med., and Godfrey Kigozi,
Both trials involved adult, HIV-negative
heterosexual male volunteers assigned at random to either intervention
(circumcision performed by trained medical professionals in a clinic
setting) or no intervention (no circumcision). All participants were
extensively counseled in HIV prevention and risk reduction techniques.
AIDS running at 4.10% in the population (according the the CIA's
World Factbook), selecting men who are HIV-negative means
are likely to have some natural immunity
are likely to be more careful than the average person and
fact that they volunteer implies they have more concern about HIV/AIDS
than others. These introduces biases that make circumcision likely to
be less effective when applied to the general population.]
Both trials reached their enrollment targets by
September 2005 and were originally designed to continue follow-up until
mid-2007. However, at the regularly scheduled meeting of the NIAID Data
and Safety Monitoring Board (DSMB) on December 12, 2006, reviewers
assessed the interim data and deemed medically performed circumcision
safe and effective in reducing HIV acquisition in both trials. They
therefore recommended the two studies be halted early. All men who were
randomized into the non-intervention arms will now be offered
statistical reasons, effectiveness of a treatment declines with the
passage of time. Cutting the experiment short gives a falsely
"It is critical to emphasize that these clinical
trials demonstrated that medical circumcision is safe and effective
when the procedure is performed by medically trained professionals and
when patients receive appropriate care during the healing period
following surgery," notes Dr. Fauci.
once the meme "Circumcision
prevents HIV" is loose in the community, this will be forgotten and
circumcisions will be done under unhygienic conditions with shared
instruments, quite possibly under
Researchers have noted significant variations in
HIV prevalence that seemed, at least in certain African and Asian
countries, to be associated with levels of male circumcision in the
community. In areas where circumcision is common, HIV prevalence tends
to be lower; conversely, areas of higher HIV prevalence overlapped with
regions where male circumcision is not commonly practiced.
correlations require highly selective use of statistics. There are many
exceptions: HIV is rare in Cuba, where circumcision is also rare, and
common in Lesotho, where circumcision is common, and common among both
the Zulu of South Africa who do not circumcise, and the Xhosa, who do.]
Results of the first randomized clinical trial
assessing the protective value of male circumcision against HIV
infection, conducted by a team of French and South African researchers
in South Africa, were reported in 2005. That trial of more than 3,000
HIV-negative men showed that circumcision reduced the risk of acquiring
HIV by 60 percent. The trial was funded by the French Agence Nationale
de Recherches sur le Sida (ANRS) (see http://www.anrs.fr/).
studies claimed an eight-fold reduction. As each new study corrects the
errors of its predecessors, the claimed benefit goes down. In this, it
resembles parapsychological research. The suspicion arises that when
all confounding factors have been allowed for, circumcision will confer
no benefit at all.
Relative Risk Reduction of 53% seems impressive, but when the rates of
HIV infection in the experimental and control populations are
considered, the results are less impressive.
infection rate in 12 months
infect. rate in 12 months
needed to treat in 1 year
(95% CI: 34-155)
words, you would have to circumcise 56 men to prevent one of
them contracting HIV in one year.
the image for an enlarged version
number needed to prevent HIV longer term is higher.
Doctors could spend their time better spent treating people with
ulcerative disease and malaria, which make HIV transmission easier
and using the money saved to promote safer sexual practices.
Few accepted medicines have such a high NNT.
On this basis, the NNT in developed countries such as the USA, where
the HIV rate is relatively low (0.6% compared to 4.1% in Uganda), would
be much higher - it would take 380 circumcisions in
the US to prevent one case of HIV.
For more information on the Kenyan and Ugandan
trials of adult male circumcision, see the NIAID Questions and Answers
document at http://www3.niaid.nih.gov/news/QA/AMC12_QA.htm.
4. What is adult male circumcision and how
was it performed in these studies?
The circumcision procedure used in the Kenyan trial was the foreskin
clamp method. ... [This is
substantially the same as the tribal method, blamed in Lesotho, where
AIDS is rife, for not taking enough mucosa] The
Kenyan trial procedure took about 25 minutes and used stitches to
control bleeding and improve wound closure. The circumcision procedure
used in the Ugandan trial is known as the sleeve method and takes about
30 minutes. [This can take
a variable amount of mucosa depending where the "sleeve" is taken from]
The Ugandan trial used cauterization of the blood vessels to control
bleeding and stitches to close the wound. Both methods are commonly
used throughout the world.
.... Both trials recruited healthy,
HIV-negative uncircumcised men who planned to remain near the study
site for the duration of the trial.
selects for any natural immunity, and weeds out itinerants, such as
truck-drivers, who are at higher risk of HIV, because of their greater
variety of partners.]
...men in the trials were cautioned to not
resume sexual activity until the
incision was fully healed and checked by the physician....
From the Manual
of Male Circumcision (October 2006), p 62
Avoid any sport, strenuous activity,
masturbation or sexual intercourse for four to six weeks. The healing
process is well advanced by 7 days but it takes 3 to 4 weeks for the
wound to become fully strong. Sexual intercourse can be started after 4
to 6 weeks, but it is best to use a condom as this helps protect the
newly healed wound. It is always wise to use a condom if there is any
risk of HIV infection. This is particularly important after
circumcision as the newly healed wound may be a weak point for two or
with the Orange Farm study,
this makes a significant difference between the
experimental (cut) and control (intact) group. The control group could
have been given a placebo operation, or another kind of placebo, and
same instructions. Even then, since the test can not be made double
blind (neither experimenters nor subjects knowing who is circumcised),
errors will occur.]
...As with most prevention strategies, adult
male circumcision is not completely effective at preventing HIV
transmission. Millions of
circumcised men have become infected with HIV through heterosexual
exposure to the virus. Men who receive adult
male circumcision may perceive that they are at decreased risk for
transmission and, therefore, may not maintain other risk reduction
strategies. Modest increases in the number of sexual partners could
negate the protective effect and increase the rate of HIV transmission
in a community. Adult male circumcision will be most effective when
integrated into a comprehensive prevention strategy which includes the
ABCs (Abstinence, Be Faithful, and Condoms) of HIV prevention.
is the Nail
Soup method of using circumcision to prevent HIV.]
The World Health Organization (WHO) press
statement in response to the NIAID DSMB recommendation is available on
the WHO web site, www.who.int/hiv.
And from http://www.who.int/mediacentre/news/notes/2006/np18/en/
UNFPA, UNICEF and the UNAIDS Secretariat emphasize that their
current policy position has not changed and that they do not currently
recommend the promotion of male circumcision for HIV prevention
purposes. However, the UN recognizes the importance of anticipating and
preparing for possible increased demand for circumcision if the current
trials confirm the protective effect of the practice.
summary critique of HIV claims.
Impact of male circumcision on the female-to-male transmission of HIV
Auvert B.1, Puren A.2,
Taljaard D.3, Lagarde E.4,
Sitta R.4, Tambekou J.4
1 UVSQ - INSERM U687 - APHP,
ST Maurice CEDEX, France, 2 NICD, Johannesburg, South Africa, 3
Progressus CC, Johannesburg, South Africa, 4 INSERM U687, St Maurice,
studies suggest that male circumcision could protect against HIV-1
acquisition. A randomized control intervention trial to test this
hypothesis was performed in sub-Saharan Africa with a high prevalence
of HIV and where the mode of transmission is through sexual contact.
Methods: 3273 uncircumcised
men, aged 18-24 and wishing to be
circumcised, were randomized in a control and intervention
group. Men were followed for 21 months with an inclusion visit and
follow-up visits at month 3, 12 and 21. Male circumcision was offered
to the intervention group just after randomization and to the control
group at the end of 21 month follow-up visit. Male circumcisions were
performed by medical doctors. At each visit, sexual behavior was
assessed by a questionnaire and a blood sample was taken for HIV
serology. These grouped censored data were analyzed in an “intention to
prevent” univariate and multivariate analysis using the piecewise
survival model, and relative risk (RR) of HIV infection with 95%
confidence interval (95% CI) was determined.
Results: Loss to follow-up was
<11%; <1% of the intervention group were not circumcised
and < 2% of the control group were circumcised during the
follow-up. We observed 45 HIV infections in the control group and 15 in
the intervention group, RR=2.77 (95% CI: 1.56 – 4.91; p=0.0005). When
controlling for sexual behavior, including condom use and health
seeking behavior, the RR was unchanged: RR=2.93 (p=0.0003).
Conclusions: Male circumcision
provides a high degree of protection against HIV infection acquisition.
Male circumcision is equivalent
to a vaccine with a 63% efficacy. The promotion of male
circumcision in uncircumcised males will reduce HIV incidence among men
and indirectly will protect females and children from HIV infection.
Male circumcision must be recognized as an important means to fight the
spread of HIV infection and the international community must mobilize
to promote it.
Some factors casting doubt on the findings:
- A summary of
the study includes this:
The experimental (circumcised) men, but not the
control group (left intact), were
Consenting to avoid sexual contact (except with condom protection)
during the 6 weeks following the medicalized circumcision
1. The circumcised experimental group, but not the
intact control group, got into the HABIT of using condoms
When you are circumcised you will be
asked to have no sexual
contact in the 6 weeks after surgery. To have sexual contact before
your skin of your penis is completely healed, could lead to infection
if your partner is infected with a sexually transmitted disease. It
could also be painful and lead to bleeding. If you desire to have
sexual contact in the 6 weeks after surgery, despite our
recommendation, it is absolutely essential that your (sic)
use a condom.
2. They learnt HOW to use condoms
3. They had to make sure they HAD condoms (which are in scandalously
short supply in South Africa), and
4. last but not least, they were PROTECTED by condoms.
The researchers could hardly say to the
experimental group, "but after that you don't have to use condoms"
Meanwhile the intact control group was not required
to use condoms for the first six weeks of the study, just sent out to
take their chances.
This throws the results into, er, a cocked hat.
- The circumcised men would have had to take some
time away from any sexual activity, reducing their exposure to HIV.
- The circumcised men would inevitably get more
exposure to safe-sex information during their time in medical hands,
waiting for and recovering from, their operations.
- Humans are not lab rats. They have sex in
non-random ways. Many of the men in the study would put themselves at
little or no risk of contracting HIV, a few at great risk, so the
effective sample size is much smaller than it appears, making the
margin of error much larger.
- Because HIV-positive men were excluded from the
study, there would have been a higher proportion of men with natural
immunity in both groups than the general population, reducing the
effective sample size still further.
- Because all the subjects did not just agree to be
circumcised but wished to be, they were not a
representative sample of the general population.
- 11-14 percent of the original participants (360 -
458 men) were lost to study or disqualified from continuing. Their HIV
status and/or circumcision status might not be typical of the total
(for example, if they dropped out because they lost interest in the
experiment when they found circumcision had not protected them),
introducing sufficient bias to refute the claimed finding.
- Michel Garenne of the Institut Pasteur in Paris
points out that the
claimed 63% efficacy is not comparable to that of a vaccine
and would result in considerable infection over time.
- Jennifer Vines, MD, of the Oregon Health &
Science University in Portland, comments
"...the authors did not control for other sources of HIV transimission
such as blood transfusions or exposure through infected needles. ...
Controlling for this route of infection could result in a smaller
difference between HIV infection rates in the circumcised versus
uncircumcised groups, indicating that circumcision may not be as
effective at decreasing HIV transmission as the article suggests."
- Columnist Stephen Strauss (below)
points out that the study was cut short before even half as many men
were infected as were infected before it began.
- The Lancet (which earlier
published a strident call for circumcision by Robert Bailey) refused to
publish the study (apparently with ethical concerns about not telling
men they had HIV). The study has been published by the Public
Library of Science, an "open source" online medium.
- The Abstract of the AIDS Conference in Rio reported
15 seroconversions from the circumcised group and 45 seroconversions in
the uncircumcised group. (The New Scientist, 6 August, reported 15
seroconversions in the circumcised group but 51 in the uncircumcised
group. On 29 July the Science and Development Network reported 18
seroconversions in the circumcised group and 51 in the uncircumcised
group.) On 23 October, PLoS reported that there were 20 seroconversions
in the circumcised group and 49 in the uncircumcised group. From the
official figures: 15-45 at the AIDS Conference in Brazil and 20-49 in
the PLoS Journal, between 1 August and 23 October there appear to have
been 4 seroconversions among the uncircumcised and 5 seroconversions
among the circumcised: in less than 3 months, a 3:1 difference has
shrunk to 2.45:1 difference.
- We've seen it many times before. Circumcision is
touted as the great panacea for this or that dreaded disease of the age
- but as the studies are refined, the advantage withers away.
- The rampant evangelism of the Conclusion suggests
that the experimenters are not altogether detached.
Even if the findings are correct:
- If they are acted on outside this controlled
setting, men with a keratinised,
reduced penis would be less likely to use condoms.
- The biggest danger, still unmeasured, is that the
mantra "Circumcision prevents AIDS" will become widespread, and
circumcised men will take no other precautions, spreading more HIV than
their circumcision prevents. Beliefs like "Sex with a virgin cures
AIDS" are already widespread in Africa. Circumcision is a painful,
memorable operation that makes a permanent, visible change to the
penis: it would be a resolute man who didn't feel it had made him safer
- and therefore act less safely.
- There is some suggestion that circumcision increases
If so, promoting it could be disastrous.
- As UNAIDS
said in 2000, relying on circumcision to protect against AIDS if it
offers only this level of protection is like playing Russian roulette
(with one bullet in the chamber instead of three).
Relying on circumcision to halt the AIDS epidemic is like fighting a
housefire with a soda-syphon.
- While a vaccine can be improved, this quite limited
preventive effect is as much as circumcision can ever possibly give.
- Rather than "Circumcision prevents HIV
transmission" it would put matters in a better perspective to say
"Circumcision (on average) delays HIV
transmission". If the findings of this study are correct, where an
intact man can expect to be infected with HIV after a year, for a
circumcised man it would take two years more.
- "Protective effect" over time depends not only on
the reduction in transmission per year, but also the incidence
(baseline rate of transmission).
Where incidence is high, as it is in Africa,
"protective effect" over time is much less than the figure for one year
- So rather than say "therefore men should be
circumcised (to make unprotected sex somewhat safer)", the message
should be "intact men should be especially sure that the sex they have
- In STATS,
Rebecca Goldin points out that the low HIV/AIDS rate in the US means it
would require 10,000 circumcisions to prevent 5.5 HIV infections, so
the risks of circumcision are at least comparable.
- This (perhaps) makes a case for voluntary adult
circumcision. Babies still have a right not to be second-guessed about
their sexual practice 16 or so years from now, the availability of a
vaccine then, or their wishes about what parts of their body they may
The misleading Relative Risk
Newspapers like big numbers and eye-catching
headlines. They need miracle cures and hidden scares, and small
percentage shifts in risk will never be enough for them to sell readers
to advertisers (because that is the business model). To this end they
pick the single most melodramatic and misleading way of describing any
statistical increase in risk, which is called the 'relative risk
increase'. [Or "Reduction"
in the case of circumcision and HIV]
Let's say the risk of having a heart attack in
your fifties is 50 per cent higher if you have high cholesterol. That
sounds pretty bad. Let's say the extra risk of having a heart attack if
you have high cholesterol is only 2 per cent. That sounds OK to me. But
they're the same (hypothetical) figures. Let's try this. Out of a
hundred men in their fifties with normal cholesterol, four will be
expected to have a heart attack; whereas out of a hundred men with high
cholesterol, six will be expected to have a heart attack. That's two
extra heart attacks per hundred. Those are called 'natural
Natural frequencies are readily understandable,
because instead of using probabilities, or percentages, or anything
even slightly technical or difficult, they use concrete numbers, just
like the ones you use every day to check if you've lost a kid on a
coach trip, or got the right change in a shop. Lots of people have
argued that we evolved to reason and do maths with concrete numbers
like these, and not with probabilities, so we find them more intuitive.
Simple numbers are simple.
The other methods of describing the increase have
names too. From our example above, with high cholesterol, you could
have a 50 per cent increase in risk (the 'relative risk increase'); or
a 2 per cent increase in risk (the 'absolute risk increase'); or, let
me ram it home, the easy one, the informative one, an extra two heart
attacks for every hundred men, the natural frequency.
As well as being the most comprehensible option,
natural frequencies also contain more information than the journalists'
'relative risk increase'.
Science" by Ben Goldacre, Fourth Estate, London (2008), p 256-9
[So here are
the natural frequencies:
The much-quoted "60% reduction" in HIV transmission after circumcision
amounts to about 12 non-circumcised men per thousand infected per year,
and about 6 circumcised men per thousand per year in those countries
the trials were held in, where HIV is rampant - far fewer where is is
rarer, such as the US.]
have a moral obligation to handle medical statistics in ways that
minimize unconscious bias. Otherwise, they cannot help but inavertently
manipulate both their patients and one another ...
Sam Harris, "The Moral
Landscape" Random House 2010, p 143
The three trials compared
So far as we know, the results of the three trials are nowhere else
presented side by side. Their figures are not always presented in
||Orange Farm, S A
||Gray, Quinn, Wawer
|HIV- at start
|Total lost from
Mar 24, 2008)
|Proportion lost from study
|“Protection” - raw
(Relative Risk Reduction)
||60% (95% CI: 32%-76%)
||55% (95% CI 22-75; p=0·002)
||61% (95% CI: 34%-77%)
||60% (30-77; p=0·003)
|Number to treat
The foreceps-guided method, in which the foreskin
is pulled forward and cut, removes significantly less mucosa than the
sleeve procedure in which a strip of tissue is taken from behind the
glans (and a method like the forceps-guided has been blamed for the
high rate of HIV infection in Lesotho, where most men are circumcised).
Yet the degree of HIV reduction is substantially the same for the two
methods - suggesting circumcision is not what is causing the difference.
Loss from study
People who drop out of trials are statistically
much more likely to have done badly, and much more likely to have had
side-effects. They will only make your drug look bad. So ignore them,
make no attempt to chase them up, do not include them in your analysis.
Science" by Ben Goldacre, Fourth Estate, London (2008), p 209
All three trials had significant numbers "lost
from study", their HIV status unknown
(yellow+orange bars in the graphs below) - 100 circumcised subjects
(6.5%) in South Africa, 87 (10%) in Kenya and 140 (3.5%) in Uganda.
(The figures are presented confusingly in the studies because the men
did not all enter the trials together, but each trial was stopped at a
Those figures are high enough in themselves to
cast doubt on the validity of the results, but circumcised men who
found they had HIV would be disillusioned with the trials and less
likely to return. It would take only 25, 25 and 23 such men
respectively to completely nullify the trials, and fewer to render the
The orange part of each of the three right-hand
bars (below the dotted lines) represents the much-hyped "60%
protection" conferred by circumcision. If just those men, whose HIV
status is unknown, proved in fact to be HIV+ (red), circumcision
would certainly have no protective effect whatever, but it
would not take all of them to reduce the effect below statistical
(One objection to this argument is that
approximately equal numbers of non-circumcised control-group members
dropped out. The answer to that is that a major and very likely
motivation for them to drop out would be completely different and
inapplicable to the experimental group - to avoid getting
circumcised. Thus what needs explaining is why nearly equal
numbers of circumcised men dropped out, and an HIV+ diagnosis could be
an answer in a significant number of cases.)
In the South African trial, one third (23 of 69)
of the HIV infections occurred in men who reported no
unprotected sex during the period from their last negative
test to their first positive test. In Uganda, 16 of 67 new infections
occurred in men who reported no sex partners (6
infections) or 100% condom use (10 infections). The trial in Kenya did
not report how sexual exposures related to HIV incidence, except for
seven men infected in the first three months (sensitive tests did not
find HIV in the men's blood at the beginning of the trial). Five of
those seven, including three of four who had been circumcised, reported
no sexual exposures from the beginning
of the trial until their first HIV-positive test.
The studies ignored exposure to HIV by
blood. In the two studies that reported information on
genital symptoms, 30-43% of infections with HIV occurred during
intervals when men reported genital ulcers or other genital symptoms or
problems. Because genital symptoms were more common in uncircumcised
men, they may have been more likely to contract HIV from skin-piercing
procedures such as injections to treat genital symptoms, but the
studies did not consider that possibility. None of the studies reported
on injections or on any other blood exposures during follow-up. In the
Kenyan trial, four men became HIV-positive a month after circumcision,
so the circumcision itself might have infected them, but the study did
not mention that possibility.
Effect of cutting the studies short
'The best of five ... no ...
seven ... no ... nine!"
If the difference between your drug and placebo
becomes significant four and a half months into a six month trial, stop
the trial immediately and start writing up the results: things might
get less impressive if you carry on.. Alternatively, if at six months
the results are 'nearly significant', extend the trial by another three
Science" by Ben Goldacre, Fourth Estate, London (2008), p 210
Randomized trails stopped early for
Montori VM, Devereux PJ, Adhikari NK, et al.
JAMA 2005; 294:2203-09
Randomized clinical trials stopped early
for benefit are becoming increasingly
common, particularly in top medical
journals. Adequate descriptions of the
methods used to inform the decision to
truncate the trial are often lacking.
Trials stopped early for
those with few events, often
report treatment effects that are larger
than typical of interventions that have
been definitively studied. These considerations
suggest that clinicians
should view results of
early for benefit with skepticism.
Stopping Randomized Trials Early for
and Estimation of Treatment Effects
Systematic Review and Meta-regression Analysis
D. Bassler, M. Briel, V. M. Montori, M. Lane, P. Glasziou, Qi Zhou, D.
Heels-Ansdell, S. D. Walter, G. H. Guyatt
and the STOPIT-2 Study Group
ALTHOUGH RANDOMIZED CONtrolled
trials (RCTs) generally
provide credible evidence
of treatment effects,
multiple problems may emerge when investigators
terminate a trial earlier than
planned, especially when the decision
to terminate the trial is based on the finding
of an apparently beneficial treatment
effect. Bias may arise because large
random fluctuations of the estimated
treatment effect can occur, particularly
early in the progress of a trial. When investigators
stop a trial based on an apparently
beneficial treatment effect, their
results may therefore provide misleading
estimates of the benefit. Statistical
modeling suggests that RCTs stopped
early for benefit (truncated RCTs) will
systematically overestimate treatment effects, and empirical data
that truncated RCTs often show
large treatment effects. ...
Theory and simulation suggest that randomized controlled trials
(RCTs) stopped early for benefit (truncated RCTs) systematically
overestimate treatment effects for the outcome that precipitated early
To compare the treatment effect from truncated RCTs
with that from metaanalyses of RCTs addressing the same question but
stopped early (nontruncated RCTs) and to explore factors associated
overestimates of effect.
Search of MEDLINE, EMBASE, Current
Contents, and full-text journal content databases to identify
truncatedRCTs up to January2007; search ofMEDLINE, Cochrane Database of
Systematic Reviews, and Database of Abstracts of Reviews of Effects to
identify systematic reviews from which individual RCTs were extracted
Selected studies were RCTs reported as
having stopped early for benefit and matching nontruncated RCTs from
systematic reviews. Independent reviewers with medical content
working blinded to trial results, judged the eligibility of the
nontruncated RCTs based on their similarity to the truncated RCTs.
Reviewers with methodological expertise conducted data
The analysis included 91 truncated RCTs
asking 63 different questions and 424 matching nontruncated RCTs. The
pooled ratio of relative risks in truncated RCTs vs matching
RCTs was 0.71 (95% confidence interval, 0.65-0.77). This difference was
independent of the presence of a statistical stopping rule and the
methodological quality of the studies as assessed by allocation
concealment and blinding. Large differences in treatment effect size
between truncated and nontruncated RCTs (ratio of relative risks
occurred with truncated RCTs having fewer
than 500 events. [The
three HIV-circumcision RCTs had a total of 196 events]
In 39 of the 63
questions (62%), the pooled effects of the nontruncated RCTs failed to
demonstrate significant benefit.
average, the ratio of RRs in the truncated
RCTs and matching nontruncated
RCTs was 0.71. This implies that,
for instance, if the RR from the nontruncated
RCTs was 0.8 (a 20% relative risk
reduction), the RR from the truncated
RCTs would be on average approximately
0.57 (a 43% relative risk reduction,
more than double the estimate of
benefit). Nontruncated RCTs with no evidence
of benefit—ie, with an RR of 1.0—
would on average be associated with a
29% relative risk reduction in truncated
RCTs addressing the same question.
suggests that the three HIV-circumcision RCTs would have showed much
less benefit - none? - if they had not been truncated. Circumcision
advocates mention the curtailing of the trials as an indication of how
beneficial circumcision is, when the reverse may be the case.]
Conclusions Truncated RCTs were
associated with greater effect sizes than RCTs not stopped early.
difference was independent of the presence of statistical stopping
and was greatest in smaller studies.
Our results have important implications
for systematic reviews and ethics. If reviewers do not note truncation
and do not consider early stopping
for benefit, meta-analyses will
overestimates of effects.
data monitoring committees
... have an ethical obligation to
future patients who need to know more
than whether data crossed a significance
threshold; these patients need
precise and accurate data on patient-important
outcomes, of both risk and
benefits, to make treatment choices.
Such patients will often number in the
tens or hundreds of thousands and
sometimes in the millions. To the extent
that substantial overestimates of
treatment effect are widely disseminated,
patients and clinicians will be
misled when trying to balance benefits,
harms, inconvenience, and cost of
a possible health care intervention. If
the true treatment effect is negligible or absent—as our results
suggest it sometimes
might be—acting on the results
of a trial stopped early will be even more
problematic. Thus, for trial investigators,
our results suggest the desirability
of stopping rules demanding large
numbers of events. For clinicians, they
suggest the necessity of assuming
likelihood of appreciable overestimates
of effect in trials stopped early.
A parallel case:
April 8, 2008
Halted drug trial safety concerns
The benefits of some cancer drugs may be
exaggerated as a rising number of trials are stopped early, experts
Italian researchers analysed 25 trials, including
some for the breast cancer therapy Herceptin, that were stopped early
between 1997 and 2007.
The Mario Negri Institute team said data from many
of the recent cases had been used to get drug licences before the
long-term impacts were known.
But drug firms said finishing trials early saved
The Annals of Oncology report showed that of the
25 trials randomly chosen, 14 had been stopped in the past three years.
And of these, 11 were used to support applications
for marketing authorisation from regulators.
Lead researcher Dr Giovanni Aplone said the
increase in early conclusions to trials suggested drug firms were using
good interim results to get their products to market more quickly.
But he warned: "Data
on effectiveness and potential side-effects can be missed by stopping a
He admitted there was no hard evidence of this,
but said there was an in-built bias
in the system because trials were often only stopped early because the
results were positive, when this
could just be a "random high".
Meanwhile, those that did not show such positive results were given
more time to prove their worth.
The team found that the
average study duration was 30 months - when the long-term impact could
only be judged over years.
The report also said some trials only enrolled
less than 40% of the total patients planned.
Researchers said regulators needed to take into
account the impact of stopping a trial early when making decisions
And they added there
needed to be more use of independent monitoring committees
to verify trial data. Only the largest trials tend to take this
Professor Stuart Pocock, an expert in medical
statistics from the London School of Hygiene and Tropical Medicine,
agreed the issue was a problem not
just for cancer drugs but all kinds of treatment.
He acknowledged trial organisers faced a dilemma
when results were positive because those patients involved in the
studies, but not receiving the therapies, could lose out.
But he added: "We need proof beyond reasonable
doubt to stop a trial early."
All three of the Random Clinical Trials of
circumcision to prevent infection of men, were cut short early,
"because circumcision worked so well". The Ugandan trial of
transmission from HIV+ men to women was cut short early
because it was "futile".
If the African studies had not been stopped early
and long-term results had been obtained, the HIV infection rate might
very well have become statistically insignificant between the
circumcised and non-circumcised groups. Look at the progression in the
number of cases of HIV in the Kisumu study:
Start of study
| Not circumcised
|0- 1 month
|1- 3 months
| 3- 6 months
| 6-12 months
The number of cases in each period for each group
is small, so their relative sizes are affected greatly by random
variation. It appears from the data that the rate of infection is lower
among the circumcised men in the first 18 months following
circumcision, but that there's little difference beyond 18 months. If
the study had not been terminated early at 24 months, it is quite
likely that the number of HIV cases between the groups would have
become insignificant. The decision to terminate the studies early
prevented any future comparison of the progression of HIV in the
circumcised and control groups and the very real possible invalidation
of the alleged "proof".
One of the researchers (Gray) has the nerve to
extrapolate the figures into the future from his truncated study,
claiming to show that the rate of "protection" increases
Circumcision could particularly benefit higher-risk men
Author: Carter M | Cairns G
Corporate Author: AIDSMAP
Source: 4 Mar 2007
Abstract: Clinical trials may
have understated the HIV prevention benefit of circumcision, according
to the lead investigator on a recently reported study. The benefit
appears to grow over time and may be highest in men with multiple
partners, the Fourteenth Conference on Retroviruses and Opportunistic
Infections heard this week in Los Angeles. As already reported, two
trials of circumcision as an HIV prevention measure for men in Rakai,
Uganda and Kisumu, Kenya were halted early last December when it became
apparent that in both trials circumcision had approximately halved the
risk of acquiring HIV. Ronald Gray, lead investigator of the Rakai
trial, gave more details to the Fourteenth Conference on Retroviruses
and Opportunistic Infections in Los Angeles last week. He said that the
benefit of circumcision was probably greater than the preliminary
efficacy of 51% would indicate. This is both because the benefit, for
reasons as yet unclear, appears to grow over time and because the
highest-risk men, namely those with multiple partners and/or with
genital ulcer disease, appeared to particularly benefit. Gray told the
conference that the protective effect of circumcision appeared to
increase over time. HIV incidence for circumcised men was 1.19% a year
from 0-6 months after circumcision [14
cases], 0.42% from 6-
12 months [5 cases]
and 0.40% from 12-24 months [3
cases]. This reduction over time was
statistically significant too (p=0.0014). The corresponding incidence
rates in uncircumcised men for the same time periods were 1.58% [19 cases],
1.19% [14 cases]
and 1.19% [12 cases].
Gray said that circumcision appeared to protect against some, but not
all, other sexually transmitted infections.
One probability is that the incidence in the first
six months is higher because they got HIV from their circumcisions! -
if there is any non-random causal relationship at all.
It is utterly innumerate to extrapolate anything
from such tiny numbers of cases, p-values or not. If he'd done the same
to the intact men, he'd find the "protection" from being intact
increased over time too!
mathematical extrapolation of that study claims that mass
circumcision "could avert 2.0 (1.1-3.8) million new HIV infections and
0.3 (0.1-0.5) million deaths over the next ten years in sub-Saharan
Africa. In the ten years after that, it could avert a further 3.7
(1.9-7.5) million new HIV infections and 2.7 (1.5-5.3) million deaths."
This has been widely broadcast around the world with new
headlines like "Circumcison could save millions - WHO" (Dominion Post,
Wellington New Zealand, July 12, 2006)) - even though the new paper is
nothing but a mathematical work up of the Auvert study, which actually
found a mere 29 (49-20) circumcised men who did not contract HIV in 21
months - compared with 20 circumcised men who did
In other words, each of those 29 men has been
extrapolated to more than 125,000 infections
and 93,000 deaths prevented - an outrageous assumption from such a
The paper's authors assume (without saying) that:
- Circumcision is cost-free and risk free
- All circumcisions are equivalent
- Circumcision has no effect on sexual behaviour
- A programme of mass circumcision will have no effect
on other AIDS-prevention programmes
- Men will volunteer for circumcision regardless of the
riskiness of their sexual behaviour.
All these assumptions are false.
has been quite invalidated by the November 2007 announcement that the number of HIV cases
worldwide is much lower than was previously estimated.
The study's authors are Brian G. Williams, James O.
Lloyd-Smith, Eleanor Gouws, Catherine Hankins, Wayne M. Getz, John
Hargrove, Isabelle de Zoysa, Christopher Dye and Bertran Auvert. Auvert
is the lead researcher of the first of the three studies (Orange Farm,
South Africa) making the claim that circumcision protects against HIV.
According to the paper, he proposed the development of the model used
and was one of those who developed and applied the model.
Auvert himself did not (at first) advocate circumcision:
Dr. Wainberg: Are we ready as a
world to make recommendations in regard to more widespread surgical
procedures such as male circumcision?
Dr. Auvert: The answer is no.
For sure we have a clear scientific answer about the association
between circumcision and HIV infection. For sure we have demonstrated
that in South Africa and this part of the world we did see a population
level reduction of HIV infection in this trial, but we are not ready to
use this as a prevention method right now. The situation in Africa is
quite complex -- you've got a lot of different cultural situations and
it's not possible.
The Lancet 2006; 368:1236
optimism for new HIV/AIDS prevention strategies
Edward Mills a and Nandi
The 2006 International AIDS Conference, showcased
in the special (Lancet) Red issue, was filled with promises for
strategies. Media attention and plenary speeches suggested that
strategies, notably male circumcision and pre-exposure prophylaxis
are imminent.1 Instead we advise cautious
drawn from the only completed randomised controlled trial (RCT) of
circumcision could be weak because
the trial stopped early.2 In a
systematic review of RCTs stopped early for benefit,3
such RCTs were found to overestimate treatment effects. When trials
with events fewer than the median number (n=66) were compared with
with event numbers above the median, the odds ratio for a magnitude of
effect greater than the median was 28 (95% CI 11-73). The circumcision
trial recorded 69 events, and is therefore at risk of serious effect
We therefore advocate an impartial meta-analysis of
individual patients' data from this and other trials underway before
further feasibility studies are done.
rationale for PREP is exciting, researchers have leapt from small
(n=6-18) and inconsistent non-randomised monkey studies
into multicentred trials.4 The first PREP trial
results were provided at
the conference,5 but had an insufficient number
of infections to provide
any inferences about effectiveness (two of 363 vs six of 368).
New interventions are required to slow the HIV/AIDS
pandemic. Disappointments stemming from media hype and
misinterpretation of early trials can make policy and recruitment of
appropriate trial populations difficult. If we are to alter the
epidemic's progress, we
should be methodologically rigorous, and cautiously optimistic about
potential for new interventions.
We declare that we have no conflict of interest.
1. Saletan W. When cutting isn't cruel. Washington
Post Aug 20 2006; B02.
2. Siegfried N. Does male circumcision prevent HIV
infection?. PLoS Med 2005; 2: e393. CrossRef
3. Montori VM, Devereaux PJ, Adhikari NK, et al.
Randomized trials stopped early for benefit: a systematic review. JAMA
2005; 294: 2203-
4. Mills EJ, Singh S, Singh JA, Orbinski JJ, Warren
M, Upshur RE. Designing research in vulnerable populations: lessons
from HIV prevention trials that stopped early. BMJ 2005; 331:
5. Peterson L, Taylor D, Clarke EEK, et al.
Findings from a double-
blind, randomized, placebo-controlled trial of tenofovir disoproxil
fumarate (TDF) for prevention of HIV infection in women. XVI
International AIDS Conference; Toronto, Canada; Aug 17, 2006.
Back to top
a. Centre for International Health and Human Rights
Studies, 1255 Sheppard Avenue East, Toronto, Ontario M2K 1E2, Canada
b. Clinical Trial Service Unit, Department of
Medicine, University of
Oxford, Oxford, UK
The Hawthorne Effect
Hawthorne effect refers to the phenomenon that when people
are observed in a study, their behavior or performance temporarily
changes. Others have broadened the definition to mean that people’s
behavior and performance change, following any new or increased
attention. The term gets its name from a factory called the Hawthorne
Works in Illinois, where a series of experiments on factory workers
were carried out between 1924 and 1932. Most notably, production went up
when the lighting was increased, and it went up
when the lighting was decreased: it was the
attention the workers were getting when the measurements were taken,
not the lighting, that caused the effect.
The Randomised Controlled Trials are subject to
the Hawthorne Effect because they were not double blind: all the
subjects knew which group they were in, and what effect this was
supposed to have. The Hawhtorne Effect could not have directly affected
the extent to which they were infected with HIV, but it could have
affected their sexual behaviour, making the circumcised men more aware
of safer sexual practises (having part cut off one's penis concentrates
the mind wonderfully), and perhaps more likely to implement them. They
reported no change in their sexual behaviour, but self-reporting may
not be accurate: their reporting of homosexual behaviour, for example,
is so low it attracts the strong suspicion that they were
A comprehensive critique:
Male Circumcision and HIV Prevention:
Really Enough of the Right Kind of Evidence?
W Dowsett, Murray Couch
"At Toronto, sociologists and anthropologists in
particular were sceptical of the narrow form of
''science'' being touted as the only form of evidence
needed. Activists and practitioners, e.g.
people living with HIV and AIDS, those working
in the non-governmental sector and prevention
workers - those who comprise the bulk of
the ''AIDS community'' - were concerned with a
potential undercutting of their hard-won shifts
in sexual cultures, in many places, toward safe
sex practices." ...
"After all, these trials were not test tube
experiments but experiments conducted in clinical
settings. Such settings are profoundly social
moments with real human interactions and complex
components, even if RCT design in principle
tries to circumvent such inputs. For example,
how do we assess the
fact of these trials not
being double-blinded: the men in each arm
clearly knew their circumcision status? That
known difference could have affected how the
men responded behaviourally, psychologically
A literature search found a much greater
proportion of the studies of circumcision were of adverse effects,
ethics, ethnology, history, legislation and jurisprudence, than (the
proportion) of the studies of appendectomy ("the surgical removal of a
part of the
body seen as somewhat unimportant") or hysterectomy ("a more serious
and controversial sexual
and reproductive health operation") .
From the conclusion:
"We believe we need to know much more about
male circumcision for HIV prevention before
adopting it as a population health measure. The
WHO/UNAIDS Statement is cautious in noting
the existence of caveats and gaps, but it argues
that it is time to go ahead. We would argue that
there is still much work to do before national
authorities and the global HIV/AIDS community
can feel confident about proceeding."
Reproductive Health Matters
Gary Dowsett was
the only person the least bit skeptical about the benefits of genital
cutting who was invited to the WHO/UNAIDS meeting at Montreux,
Switzerland in 2007 where genital cutting was set as a mass
intervention to protect against HIV. As Intactivists suspected, the
meeting was gerrymandered by circumcision advocates Daniel Halperin,
Robert Bailey, Robert Gray and others to rubberstamp their
How the WHO was manipulated into promoting genital cutting as an HIV prevention
Global Public Health,
Hybrid forum or
network? The social and political construction
of an international ‘technical consultation’:
Male circumcision and HIV prevention
Alain Giami, Christophe Perrey, André
Luiz de Oliveira Mendonça & Kenneth Rochel de Camargo
consultation in Montreux, organised by World Health Organization and
UNAIDS in 2007, recommended male circumcision as a method for
preventing HIV transmission. This consultation came out of a long
process of releasing reports and holding international and regional
conferences, a process steered by an informal network. This network's
relations with other parties is analysed along with its way of working
and the exchanges during the technical consultation that led up to the
formal adoption of a recommendation. Conducted in relation to the
concepts of a ‘hybrid forum’ and ‘network’, this article shows that the
decision was based on the formation and consolidation of a network of
persons. They were active in all phases of this process, ranging from
studies of the recommendation's efficacy, feasibility and acceptability
to its adoption and implementation. In this sense, this consultation
cannot be described as the constitution of a ‘hybrid forum’, which is
characterised by its openness to a debate as well as a plurality of
issues formulated by the actors and of resources used by them. On the
contrary, little room was allowed for contradictory discussions, as if
the decision had already been made before the Montreux consultation.
There was but one avowed opponent in this group: Gary Dowsett, an
Australian sociologist who had extensive experience in social science
research on AIDS and had served as consultant for WHO and other
international organisations. As one of a group of self-identified gay
researchers, his activities in this field reached back to the mid-1980s.
Nonetheless, the possibility for him to present his critique was limited
by both the agenda and the perceived hostility towards him during
discussions by, in particular, a major US epidemiologist,
one of the recommendation’s principal advocates.
During our interview, Dowsett cited this person’s name, which we have
replaced with the pronoun HE in the transcripts:
I’m standing in the hotel, with a glass of champagne and HE …
comes charging over to me, immediately … and just started to attack me,
immediately, and … ‘How wrong I was! Why I was doing this? I got the
argument wrong – Did I not understand how important all this was’ …
and HE attacked me … every time I spoke in the meeting at Montreux.
According to some interviewees, the time devoted to the presentations
did not allow for a genuine, open debate, in particular about how to
extrapolate from the findings in the narrow context of the RCTs
to the general population. This question was thought to be settled,
given the results from previous observational and epidemiological studies.
There was no mention of the contradictory findings that had been published,
nor of a scientific controversy. According to Dowsett during our interview,
Hankins’ speech on the second day barely mentioned the recommendation’s
social and cultural consequences:
We were concerned about the cultural consequences of circumcision
in terms of shifting ideas of sexuality, sexual cultures and masculinity;
and any evaluation of circumcision being rolled out needed to include
much broader social and cultural markers than simply medical and behavioural
markers of the implementation. That was part of the recommendations
for the research agenda, from the social science meeting in Durban.
That was simply reported in Montreux, and nothing was either endorsed
or done about it. It was just presented as background information.