My patient, a 51-year-old commercial fisherman, was looking a bit confused. I had just finished his annual physical exam and was checking off the various screening tests on his lab requisition. When I got to the box for prostate cancer screening, I hesitated’as I always do. The publication of two landmark studies in the past year in the New England Journal of Medicine shows significant limitations for standard prostate cancer testing.
The problem with screening for prostate cancer
Prostate cancer is the second most diagnosed cancer in men (after non-melanoma skin cancer), and the third most common cause of cancer death (after lung cancer and colorectal cancer). This year 26,500 Canadian men will be diagnosed with prostate cancer and 4,000 will die from it.
Screening for prostate cancer would seem like a no-brainer for doctors to order. But the PSA (prostate-specific antigen) test, which is the best current screening and involves a blood test, has three significant shortcomings:
False positives: The majority of men with an abnormal PSA’about 80 percent’don’t have the disease. That means a lot of unnecessary anxiety.
Over-diagnosis: An abnormal PSA typically requires further testing’usually biopsy or ultrasound. Both are uncomfortable, are expensive for the healthcare system and can cause problems such as infection.
Over-treatment: Surprisingly, about 75 percent of prostate cancer cases are not fatal even if left untreated, while 25 percent are aggressive killers. But we can’t yet reliably distinguish between them, since we don’t understand enough about the genetics of cancerous prostate cells to accurately predict whether they will progress. Surgery, radiation and hormone therapy have significant side effects such as incontinence, infection and permanent impotence. Knowing the risks and the fact that a majority of these cancers will not spread or kill, many physicians and patients opt for a strategy called ‘watchful waiting,’ in which an elevated PSA level is tracked every three to six months and treatment is recommended only if there is a rapid or large rise (suggesting the cancer may be an agressive one). Not surprisingly, the idea of knowing you have cancer and not treating it makes many men’and their physicians’very uncomfortable.
To add to the confusion, major groups in Canada and the U.S. offer different recommendations; the respective urological associations favour routine testing after age 50. But the Canadian Task Force on Preventive Health Care and the U.S. Preventive Services Task Force recommend against screening based on the latest evidence, which indicates the benefit of routine screening may be outweighed by the harm.
So what to do?
First, remember that even the big proponents of regular screening in both Canada and the U.S. recommend routine testing only if you are at least 45 to 50 years old. Until there’s a better test, I have some general suggestions:
Know your risk factors: There are two kinds of risks: avoidable and unavoidable. In terms of avoidable, you’ve heard it all before: Eat less saturated fat, get more fibre. Exercise more (aiming for 30 minutes daily) and maintain a healthy body weight. The risk factors you’re stuck with include age (the majority of prostate cancers are diagnosed over age 65); ethnicity (the disease is more common and more fatal in blacks, less common in whites and least common in Asians); and family history’risk is significantly higher if you’ve had two or more relatives diagnosed, and it’s particularly high if a first-degree relative (father, brother) was diagnosed when younger than 65.
Get the digital rectal exam: This is recommended each year starting by age 50, but request it earlier if you have risk factors.
Balance the risks of certainty and uncertainty: Talk to your doctor about the implications of false positives, over-diagnosis and over-treatment.
If you do get tested, reduce the risk of a false positive: Certain things increase PSA levels, including low-grade trauma to the prostate (such as a recent rectal exam or even a long bike ride!) and ejaculation. Avoid all for at least 48 hours before the test.
Decide your next step before the test: To avoid freaking out, ask your doctor what the plan will be if the test is abnormal. Perhaps the easiest path is simply to re-test, but wait at least six weeks. And as hard as it may seem, try to stay calm.
Dr. Chris Watt is a GP and sports medicine physician who practises in Victoria and Vancouver.