Evidence does not support blanket prostate cancer testing recommendation
Earlier this week, Prostate Cancer Canada released a recommendation that all men have a baseline PSA test in their 40s. This recommendation is based in part on a recent paper by Vickers and colleagues in the British Medical Journal that showed that men in their 40s with a relatively high PSA level have a higher-than-average risk of developing metastatic prostate cancer. I do not believe this evidence is strong enough to support a blanket recommendation of this kind.
Prostate Cancer Canada is an important patient organization and its views matter in the popular press and with men who have had prostate cancer. Through the media, its views may also influence many physicians. It is also a fair to say that relative to breast cancer, the major cancer in women, Canadian investments in prostate cancer research are small: less than half of breast cancer. It is also incontrovertible that men would like to have the benefits of an effective screening procedure for prostate cancer.
While five year survival from prostate cancer diagnosis in Canada now exceeds 95%, this is cold comfort to those men who die prematurely from the disease, typically with painful metastatic disease. On the other hand, roughly one in six men will be diagnosed with prostate cancer during our lives, yet only about one in 36 will die from this disease. Most of us men north of 60 will have a low level of malignancy. The existence of such frequent latent cancers may sound alarming, but many cancers grow slowly, and as a result we are more likely to die with prostate cancer rather than from prostate cancer.
Nevertheless many men hearing the argument for early PSA testing will understand its logic: we believe early detection of prostate cancer is best. But is it?
Let’s consider what we currently know. Two large and long awaited trials emerged in the last five years, one US and one European on the benefits of early detection of disease with PSA. No benefit was seen in the US trial. The benefit in the European trial, which was well done, showed that over 1400 men have to be screened and about 50 of them have to undergo treatment in order to save one life.
Well you might ask, is this not worth it, isn’t saving one life priceless? For large scale screening to be effective, however, the benefits must outweigh the harms.
In the case of prostate cancer testing with PSA, most thoughtful preventive health service authorities would say that routine mass screening using PSA has more harms than benefits. These harms come in the form of common but rarely serious problems of bleeding and infection following trans-rectal ultrasound biopsies to test for cancer (the PSA test provides information about risk only) as well as in the harms associated with treatment, such as impaired sexual function and urinary incontinence.
Here is the final challenge, what has been called the “popularity paradox”. Once screening becomes widespread, people who have early stage disease detected and treated successfully often believe fervently they have been saved premature death from the disease, when it will be only the tiny minority who live longer because of testing. The remainder will have had in most cases slightly long, anxious and unnecessary careers as cancer patients being monitored or treated, more or less aggressively, for a disease which in the majority of cases will not have brought on their untimely death.
When it comes to screening, a dollar spent on a test for asymptomatic men who will not die of the disease is a dollar not spent on finding better detection, predictive tools and treatments for more virulent and lethal prostate disease.
Prostate Cancer Canada serves a very valuable function by funding prostate cancer research. A better understanding of why some men develop lethal prostate cancer and others do not may eventually lead to a screening strategy that clearly has a more favourable benefit-to-harm ratio.
In the meantime, men who are at high risk because of a family history or because they have symptoms are candidates for PSA testing. Others who are concerned should discuss the potential benefits and harms of testing with their physician or learn more about the issue themselves. Some well informed patients will choose to undergo PSA testing, but others will not. In the face of weak evidence, either decision is reasonable. But the evidence is almost certainly not strong enough for a blanket recommendation that all men in their 40s have a baseline PSA.
Terrence Sullivan is an editor of Healthy Debate, the former CEO of Cancer Care Ontario and the current Chair of the Board of Public Health Ontario.