October 14, 2011
National Panel Advises Against Prostate Cancer Screening
Every year in the US over 200,000 men are newly diagnosed with prostate cancer, and every year 30,000 men die of the disease. With a problem this common that kills so many, you would think that aggressive testing of healthy men is certain to save lives.
Whether screening for prostate cancer has any benefits has always been controversial. By the way, screening means testing for a disease in a patient without any signs or symptoms of the disease. It means testing healthy members of the general population. The test typically used to screen for prostate cancer is a blood test called PSA (prostate specific antigen).
There are three reasons that screening for prostate cancer is particularly problematic. First, it tends to happen in older men. It’s very rare before the age of 50, but three fourths of men older than 85 are found to have it on autopsy. The second reason is that most prostate cancer is very slow growing, and takes over a decade to cause any harm. That means that most men who develop prostate cancer are unlikely to ever be bothered by it and will die of some other cause. So diagnosing those men’s prostate cancer doesn’t help them, but exposes them to all the harms of prostate cancer treatment and all the anxieties related to being a cancer patient. Finally, the PSA is notoriously inaccurate and is frequently abnormal even in the absence of cancer, leading to many negative prostate biopsies.
The national body charged with evaluating which preventive tests are beneficial and which are not is the US Preventive Services Task Force (USPSTF). Three years ago the USPSTF recommended against screening for prostate cancer in men over 75 and said that for men between 50 and 75 there was insufficient evidence to recommend for or against screening. Even the American Cancer Society which represents oncologists (and is therefore about as unbiased about cancer screening as auto mechanics are about regular car tune-ups) last year retracted its unqualified support of prostate cancer screening.
This week in an article in the Annals of Internal Medicine the USPSTF reviewed new evidence and revised its recommendations, recommending against prostate cancer screening in men of any age. The panel concluded that
“prostate-specific antigen–based screening results in small or no reduction in prostate cancer–specific mortality and is associated with harms related to subsequent evaluation and treatments, some of which may be unnecessary.”
Prostate cancer advocacy groups and survivors are already up in arms criticizing the finding, and some are politicizing the issue by claiming that this is an attempt to ration care. But let’s look at the actual data before we pick sides.
Of all the studies to test whether PSA screening saves lives the two biggest and best-designed had conflicting results. One study in the US showed that PSA screening did not save lives. The other, a European trial, found a small benefit. It found that one life was saved from prostate cancer for every 1,410 men checked periodically with a PSA.
So let’s imagine a group of 1,410 men in their 50s and 60s sitting in the local school auditorium trying to decide whether or not to be screened. One study showed that there are no lives saved from screening, in which case there is no reason to do it, but for the sake of argument, let’s accept the findings of the more optimistic trial and agree that testing all of their PSAs periodically will save one of their lives.
What harms will we cause them through screening? Well, first there will be about 12% of them with false-positive PSAs, meaning abnormal PSAs but no cancer. That means 176 of them will be put through biopsies to prove they don’t have cancer. About one of these men will develop a serious complication from the biopsy and require hospitalization.
48 of the men will end up being diagnosed with prostate cancer and will undergo treatment. (But remember only one life will be saved. That’s because the other 47 either die of a cause other than prostate cancer, and thus do not benefit from screening, or died from prostate cancer despite being screened.) Given some reasonable assumptions about the treatments chosen by patients, 36 of them will have a prostatectomy and 12 of them will undergo radiation. That will lead to 14 men having erectile dysfunction and 7 having urinary incontinence. Not to mention that each of the men having prostatectomy have a 1 in 200 chance of dying due to the surgery.
That’s a lot of harm for, at best, very little good, and possibly no good at all. This recommendation should prompt patients and doctors to rethink their opinions about screening and have another conversation about it.
U.S. Panel Says No to Prostate Screening for Healthy Men (New York Times)
Panel Faults Widely Used Prostate-Cancer Test (Wall Street Journal)
Screening for Prostate Cancer: A Review of the Evidence for the U.S. Preventive Services Task Force (Annals of Internal Medicine)
Surgery Might Save Lives in Early Prostate Cancer (my most recent post about prostate cancer with links to previous posts)
Important legal mumbo jumbo: