Tuesday, March 13, 2012

Overhyped research on prostate cancer & circumcision link

Yesterday Twitter was abuzz with tweets about a new study that showed an association between circumcision and a lower risk for prostate cancer. You wouldn’t know that it was just an association by the headlines.Here are but a few.

Circumcision Cuts Prostate Cancer Risk Scientific American
Circumcision reduces prostate cancer risk UPI
Circumcision Linked to Lower Risk for Prostate Cancer, Study Finds Yahoo News

And my favorite,

Males of the Mideast Rejoice: Circumcision Reduces Prostate Cancer Asian News International

In fact, not only is it just an association, it is a very weak association at best.

The research was a retrospective case-control study of men who self-reported their circumcision status, sexual histories and other information. There were 1754 men with and 1645 without prostate cancer in the study. The numbers of circumcised men differed by only 2.7% [1207 (68.8%) with cancer vs. 1176 (71.5%) without cancer.}

The relative risk of developing prostate cancer was not significantly different in circumcised and uncircumcised men until the authors looked at those who had been circumcised after their first episode of sexual intercourse. The numbers of men who had been circumcised after their first sexual encounter was only 68 (3.9%) of the men with prostate cancer and 41 (2.5%) of those without. Although the relative risk reduction was 15%, the confidence intervals were wide (73% to 99%) and were just barely significant.

And don’t forget, this is a relative, not an absolute, risk reduction of only 15%.

Most of the paper’s discussion involved circumstantial evidence that because infection has been linked to some cancers, infection of the prostate or penile skin may possibly play a role in the development of prostate cancer.

So does circumcision actually reduce the risk of contracting prostate cancer?

It shouldn’t surprise anyone, but I am skeptical. Do you really believe that one act of sexual intercourse before a man is circumcised would really have an impact? What if the man did not develop an infection after that episode or any subsequent episodes?

Don’t believe me? Here is a quote from Internal Medicine News, which not only had a more subdued headline, it published one of the few articles that featured the opinion of an outside expert, Dr. Stephen J. Freedland, a urologist at Duke. He said:

"This study provides modest evidence: a 15% reduction. It’s not as if we should recommend that every baby be circumcised because it can reduce prostate cancer by 15%. This is more of a research finding,"

Those males of the Mideast should probably temper their rejoicing until some more solid evidence appears. Meanwhile, they may want to consider a study from 2003 suggesting that masturbating may prevent prostate cancer.

14 comments:

Yeoman Roman said...

How about just calling these "fishing expeditions" what they are, Exaggerations and lies.

Franny said...

Excellent post! Do you consider yourself to be an intactivist? Please write more about the functions of the foreskin, and complications from circumcision. Ten out of ten babies oppose circumcision!

Skeptical Scalpel said...

Thanks to both of you for commenting. I have always thought circumcision was barbaric. I have three sons who are not circumcised.

Hannah said...

Yes, I would say it was more of a "survey" than actual research, and didn't control for any other factors. Besides, a small reduction in a far-off disease isn't a good reason to cut off a body part.

Skeptical Scalpel said...

Hannah, thanks for commenting. I agree.

Dr Robert Darby said...

It's amazing how any study that appears to show the foreskin in a bad light gets worldwide publicity, when journal articles critical of circumcision and statements against the practice from responsible medical authorities are ignored. The Royal Australasian College of Physicians examined the putative lack of circumcision-higher risk of prostate cancer link in its 2010 policy, and found the evidence to be lacking (See http://www.racp.edu.au/page/policy-and-advocacy/paediatrics-and-child-health for the full policy.) There have been at least half a dozen studies since the 1950s on the question, none of which have found any association at all. (See http://www.circumstitions.com/cancer-pros.html for details) This latest study does not suggest circumcision as a means of further lowering the risk (already quite small) of prostate cancer, but is most interested in a related question: the contribution of infection with human papilloma virus (HPV) to the risk of developing prostate cancer. There is a widely held belief that circumcised men are less likely to be infected with HPV, a view based largely on studies in Africa, but not confirmed by studies in the developed world; the most recent study, by Van Buskirk et al, found no difference. (See http://www.circinfo.org/news_2011.html#busk for details.) The whole sorry exercise seems to be just another chapter in the long history of the demonization of normal male anatomy.

Hugh said...

Your skepticism hits the spot, especially when we are talking about circumcising scores of babies to prevent one man getting prostate cancer 70-80 years from now. Given the state of medicine in 1932 compared to today (and the exponential growth of science), it's ridiculous to imagine we can second-guess the future so much.

There have been even worse headlines than the ones you quote, such as "The rabbi was right: prostate cancer prevention from birth" Circumcision has ever been a "cure" looking for a disease, and after penile cancer, then cervical cancer and now prostate cancer, can breast cancer be far behind?

Skeptical Scalpel said...

Hugh, Thanks for the comments. I agree.

Anonymous said...

You forgot to point out that circumcision status was based on the subject's report, which can be wrong between 5% and 15% of the time. This means that the difference found in this study could easily be from a misclassification bias. Any other topic, or if they found circumcision has no association, and this study would never have been paid for or published. The bar is lower for studies that promote circumcision.

Skeptical Scalpel said...

Yes.The authors of the study did point out that as hard as it is to believe, some men don't really know whether they've had a circ or not.

Anonymous said...

Almost all males will develop prostate cancer if they live long enough. All the males with prostate cancer I have cared for as a physician have been circumcised. This is just another attempt to demonize the foreskin and persuade parents, physicians and politicians to mandate infant circumcision, which is truly a human rights violation. More males die from circumcision than will be saved from prostate cancer if circumcised. This is like the hype about tomatoes decreasing prostate cancer. It is just an association or observation and has no clinical relevance overall. Shame on those researchers and the media for once again distorting the reality of the situation in order to promote a barbaric stone-age ritual.

Skeptical Scalpel said...

Anonymous

Thanks for commenting.

RD said...

Middle aged American men with university degrees, the American chattering class, may be 95-985 circumcised. Is it any surprise that the main country whose media touted the alleged association between the foreskin and prostate cancer, is the USA?

I am much warmer to the hypothesis that men who masturbate are less likely to experience prostate cancer. It is also the case that masturbation is easier and more pleasant when the penis is left in its natural state. Ergo...

Skeptical Scalpel said...

RD, thanks for commenting. This sort of research and reporting drives me crazy.

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