Subscribe to the OSS Weekly Newsletter!

Prostate Cancer and the Problem With PSA Testing

False positives, over-diagnosis and a stable mortality rate raise doubts about this kind of screening for healthy men.

This article was first published in The Montreal Gazette.

Get ready. Come November, men will start growing out their moustaches. The stated goal is simple. They want to raise awareness about prostate cancer and want to encourage men to get their PSA level checked. But some people (generally the women who have to look at the men with moustaches) are not fans of the moustaches and feel they are unnecessary. Ironically, the PSA screening may be unnecessary too.

Prostate specific antigen, or PSA, is a protein produced by cells in the prostate. Measuring PSA levels became widespread in the late 1980s as a way to detect early stage prostate cancer. In one sense, the test was very successful. The number of new prostate cancer diagnoses per year rose sharply after PSA screening started.

But in another sense, PSA screening failed to do something that was even more important. While new cancer diagnoses went up, cancer deaths stayed pretty much stable. In fact, the 2013 Cochrane review on the subject of PSA testing found no improvement in mortality. While one study, the European Randomised Study of Screening for Prostate Cancer, did find a reduction in prostate cancer deaths after 13 years of follow-up, mortality only decreased by 0.1 per cent. It is generally felt that if there is any mortality benefit to PSA testing, that benefit is likely very small. Consequently the Canadian Task Force on Preventive Health Care actually recommends against PSA testing as a way to screen for prostate cancer, although other groups like the USPSTF suggest it can be considered in some cases.

The problem with PSA testing is essentially one of false positives. While prostate cancer cells produce PSA, so do normal prostate cells. So PSA levels can fluctuate a fair degree from one measurement to the next. Also, many things other than prostate cancer can cause a spike in PSA levels. An infection of the prostate, called prostatitis, can cause a spike in PSA levels as can recent sexual activity. What constitutes a normal PSA level changes with age and bodyweight and many medications used to treat an enlarged prostate can lower PSA levels.

PSA levels can also be elevated when men have benign prostatic hyperplasia (BPH). With age, the prostate gland grows and begins to obstruct the outflow of urine from the bladder, leading to increased trips to the washroom throughout the day and night. Thus, rising PSA levels might be due to BPH rather than a cancer diagnosis. Suffice it to say, interpreting a PSA test is not necessarily easy and many men, roughly one in five, will have a false positive and an unnecessary biopsy.

The other problem is one of over-diagnosis. Even when PSA levels do detect cancer, they will often pick up a low-grade non-aggressive cancer that will probably never spread. Treating these men with surgery, radiation and chemotherapy would probably be unnecessary since these types of prostate cancer usually don’t metastasize or cause symptoms. Had the PSA testing never been done, these men might have been blissfully unaware of their diagnosis and died at a ripe old age of something else. In fact, the five-year survival rate of prostate cancer is quite high at 98 per cent. Therefore, aggressive treatments for these low-risk cancers may not be appropriate and active surveillance, a policy of observation and close follow-up, is generally preferred in these cases.

It is important to note that we are talking about screening for prostate cancer, which means testing men with no symptoms who are otherwise well. PSA testing does have some role in following men with symptoms or confirmed prostate cancer to monitor response to treatment. But for the vast majority of the population, PSA testing has uncertain benefits that might be outweighed by the risks and complications of unnecessary biopsies and treatments. Although, it is often hard for people to do nothing, it is worth remembering the old adage. Most men die with prostate cancer, not of prostate cancer.


Want to comment on this article? Visit our FB Page!


Back to top