Very Swedish study on prostate cancer, part 2
In Guteborg, the second largest city in Sweden, scientists and doctors have been orchestrating one of the longest lasting studies on prostate cancer screening.
According to the CDC, 13 out of 100 Americans will be diagnosed with prostate cancer during their lifetime, and 2-3 out of 100 Americans will die from the disease.
The most widely used test to screen for prostate cancer is a blood test called PSA. In my last article, I told you about Guteborg, about prostate cancer, and about PSA.
And I summarized by saying the following: prostate cancer is a prevalent disease that is potentially lethal, but most patients will die with prostate cancer rather than from it; and PSA–the most frequently used test in prostate cancer screening–is an imperfect tool where a positive test may or may not indicate a serious, potentially life-threatening cancer.
Does screening for prostate cancer save lives? And at what cost? Today I will try to answer these questions by looking at the information gathered by the Guteborg study.
The study began in 1994 when 20,000 Swedish men were randomly assigned to either a screening group or a control group. The men in the screening group were invited (repeatedly, every other year) for PSA testing, and those who had elevated PSA were invited for further evaluation including prostate biopsies.
Men in the control group weren’t invited for PSA testing, but were, at times, exposed to “opportunistic” PSA testing (their doctor decided, independent of the study, to check their PSA).
The researchers followed the participants in both groups for a long, long time–22 years to be exact. In the group that had PSA screening, the chance of being diagnosed with prostate cancer was higher: 1,528 men in the screening group were diagnosed with prostate cancer compared with 1,124 in the control group.
Did PSA screening save lives? The results suggest that PSA screening led to a significant reduction of death from prostate cancer. Of the men in the screening group, 112 died of prostate cancer compared with 158 deaths attributed to prostate cancer in the control group.
The absolute reduction in prostate cancer death was 0.59% (from 2.13% in the control group to 1.55% in the screening group).
The results of the Guteborg study also suggest that when it comes to death of any cause (as opposed to death attributed to prostate cancer), the benefit of screening seems to disappear: 3,806 men in the screening group died of any cause (including prostate cancer, but also heart disease, stroke, etc.) compared with 3,735 in the control group.
According to this study, in order to save one man from dying of prostate cancer, 221 men would have to be invited for screening, and 9 men will have to be diagnosed with prostate cancer. These numbers are important because the diagnosis and treatment of prostate cancer aren’t inconsequential: in order to make the diagnosis, a man has to undergo prostate biopsy which is unpleasant and can result in bleeding, and, at times, severe infection. Once prostate cancer is diagnosed, things may get even more complicated. First, the diagnosis carries significant emotional burden. And, depending on the severity of the disease, a man can choose from three main options: active surveillance that comes with uncertainty, anxiety, and the risk of disease progression; and treatment with surgery or with radiation therapy that carry significant side effects including urinary incontinence, lower urinary symptoms, and erectile dysfunction.
The Göteborg study joins several other long-term studies examining the effect of prostate cancer screening. The results are mixed and there are no absolute, clear answers. The results are mixed because they are highly dependent on the methods the researchers use in their pursuit of the truth. If the control group is “contaminated” (by participants in the control group who nevertheless are exposed to PSA testing), the results are less impressive in terms of saving lives. Also, the benefit of diagnosing prostate cancer is highly dependent on whether treatment for prostate cancer is rendered, and how effective it is. What good is it to diagnose a potentially lethal disease if you aren’t going to treat it effectively?
PSA screening is, like I had written here before, an imperfect tool. The Swedish study has shed some additional light on the complexities involved in prostate cancer screening. For now, I believe the following to be true: PSA screening, as opposed to no screening at all, can decrease the chance of death from prostate cancer. It comes with high costs though: the hassle and the financial cost of screening, the anxiety embedded in the diagnosis of cancer, the cost and side effects of surgery and radiation; and the risk of diagnosing and treating a disease that, in many cases, would remain inconsequential.
EDITOR’S NOTE: Dr. Shahar Madjar is a urologist at Aspirus and the author of “Is Life Too Long? Essays about Life, Death and Other Trivial Matters.” Contact him at firstname.lastname@example.org.