About 20 years ago a blood test called prostate specific antigen (PSA) was developed with the hope that it would help in the diagnosis of prostate cancer. Since then, countless healthy men have been tested for prostate cancer with a PSA and a digital rectal exam despite the fact that there has never been convincing evidence that diagnosing prostate cancer saves lives.
The reason for the controversy about prostate cancer screening is that prostate cancer is a very slowly growing cancer which usually takes a decade or longer to be life-threatening. Prostate cancer also occurs in older men. So many cases of prostate cancer never cause symptoms and do not shorten lifespan. The treatments for prostate cancer, on the other hand, can involve serious and permanent side effects, including urinary incontinence and erectile dysfunction.
The most important question about prostate cancer screening has always been does it save any lives? And if it does, is it worth putting men through potentially harmful treatment now for the possibility that we’re saving their lives 10 years from now?
Two studies released this week in the New England Journal of Medicine unfortunately don’t help clear the fog, and have generated much media attention. (See links below.) The first study was a randomized trial in the US which showed that prostate cancer screening did not prevent any deaths from prostate cancer. This study, however, had some serious methodological flaws.
The second study randomized over 100,000 men in Europe into two groups: one which received periodic prostate cancer screening, and one which did not. The results showed a tiny mortality advantage 9 years after being screened. There was one life saved for every 1410 men screened for prostate cancer and for every 48 men treated for prostate cancer. That’s not a very compelling benefit. It means that 47 men are harmed by prostate cancer treatment for every life saved and that screening an individual has a smaller than 0.1% chance of helping him. Given this tiny benefit, it’s difficult to say if more harm was done than good.
The US Preventive Services Task Force states that the evidence is insufficient to recommend for or against screening for prostate cancer in men age 50 to 75. It recommends against screening men older than 75. For men between 50 and 75 that still means a discussion with their physicians about the possible risks and uncertain benefits of screening, and then making a personal decision without much scientific guidance.
NY Times editorial: The Prostate Cancer Muddle
LA Times article: Studies cast doubt on prostate cancer screenings
The two New England Journal of Medicine articles: Mortality Results from a Randomized Prostate-Cancer Screening Trial and Screening and Prostate-Cancer Mortality in a Randomized European Study