Norman Geras discusses a US decision to advise against PSA testing for prostate cancer:
I’m in no position to comment on the medical evidence either way. But men who discover they have prostate cancer too late to benefit from curative treatments are unlikely to be convinced by the arguments against screening. Most of them will prefer to have had a PSA test in good time and, after getting the result, to have been able to weigh the options before them in the light of the known risks.
The US decision is in line with the current evidence presented at the Cochrane review, and general concerns that PSA testing may expose men to curative treatments that will cause severe adverse effects. In older men these adverse effects may severely damage their quality of life, when they well have died from some other cause before the prostate cancer would have had an equivalent, or even any, negative effect.
I’m not arguing with Norman’s point that most men would prefer to be able to weigh the options before them. My quibble is that of timing. Men should weigh the options before they have the PSA test, not after. Gerd Gigerenzer in his excellent book Reckoning with Risk, discusses his economist friend’s reaction to PSA testing.
“It can’t hurt,” responded my friend. He simply assumed that screening has no costs. He erred again, there is no free lunch here. The test produces a substantial number of false positives, and therefore when there is a suspiciously high PSA level, in most of these cases there is no cancer. That means, many men without prostate cancer may go through unnecessary anxieties and often painful follow-up exams. Men with prostate cancer are likely to pay more substantial costs. Many of these men undergo surgery or radiation treatment that can result in serious lifelong harm such as incontinence or impotence. Most prostate cancers are so slow growing that they might never have been noticed except for the screening. Autopsies of men older than 50 who die of natural causes indicate that about one in three of them have some form of prostate cancer. More men die with prostate cancer than from prostate cancer.
Cancer Backup reflect this dilemma in their advice on the pros and cons of PSA testing:
Possible advantages
- It could reassure you if the test is normal
- it can help to find cancers before any symptoms develop
- treatment in the early stages could help you live longer and avoid the complications of cancer (although there is no good research evidence that this is so).
Possible disadvantages
- It could read normal when there is cancer in the prostate, and falsely reassure you that all is well
- it could lead to anxiety, even though you have no cancer
- it could lead to a biopsy, even though you have no cancer
- if you have cancer it can’t tell you if it is likely to cause problems in the future
- treatment of early prostate cancers might not help you live longer
- treatments for early prostate cancer have risks and may cause side effects that can affect your quality of life.
Screening tests are not neutral decisions. They carry risks. Weighing the options should include the initial decision to undergo a PSA test, as well as future treatment decisions.