A cancer problem switches gender

The New York Times recently printed a valuable article discussing the PSA screening test for prostate cancer. I previously discussed the statistics of this test here.

The entire article is worth reading. Here, I summarize the key issues:

• Prostate cancer is a slow-growing cancer, which means that many men die with it, rather than die from it. This means that autopsies will identify many men with prostate cancer, many of whom did not die because of it. If these men were to have received treatment in their lifetime for prostate cancer, they would still have died the same way they died.
• Detecting prostate cancer late in life is rather useless because many men would have died from other causes before these cancers could have killed them.
• Screening tests always generate many false positives. The false positive rate depends on the proportion of those tested who actually have the ailment: there are more false positive errors when the tests are given to people who are less likely to have the ailment. Thus, the younger men taking PSA tests will suffer a higher chance of false positives.
• If you are given the knowledge that there is a chance you have prostate cancer (even if it is a small chance, say 30%), you may elect to do a biopsy to buy yourself "peace of mind". Likewise, the doctors may want to insure themselves against future negligence lawsuits, or may simply want to earn the fees associated with the surgeries.
• Since most of those being treated are false positives, the treatment will have zero benefit, and some unlucky patients will suffer side-effects.
• False positive is a laboratory term. Your test result is a positive, period, not a "false" positive. You must make the decision whether to treat it or not - and risk side-effects - before you find out if it is a false positive. (If you know it is a false positive, then you already know you don't have cancer, which means you don't need to be screened in the first place.)
• The PSA screening test is a multi-billion-dollar industry.
• These are the same issues raised during the mammography controversy. One ought to be consistent and gender-neutral in the way one approaches each.

These concepts were covered in Chapter 4 of Numbers Rule Your World.

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While the article is great, the title is not. In the print edition, it is called "Screening prostates at any age". The article is primarily concerned with whether elder men should be screened at all.

Comments

[Ken]

A good read is http://ses.library.usyd.edu.au/handle/2123/6835 Note that this is Australian so the costs of treatment are much lower than the US and Medicare refers to the Australian public health system.

[Prostate Cancer]

It's great to see these facts regarding prostate cancer. Too often people think about women when it comes to cancer, at least this article shows that even the male segment of the population are susceptible to diseases.