Doctors Debate the Pros and Cons
Doctors Debate the Pros and Cons
By Wayne Kuznar
TORONTO, Canada—Prostate cancer screening using prostate-specific antigen (PSA) represents a conundrum for most physicians. PSA screening may expose patients to further testing and biopsy, and even when a cancer is detected, it may not prolong survival.
At the Society of General Internal Medicine annual meeting, John Concato, MD, MS, associate professor of medicine at Yale University and director of the Clinical Epidemiology Research Center at the VA Connecticut Healthcare System, West Haven, and Neil Fleshner, MD, chief of urology, University Health Network and Princess Margaret Hospital, University of Toronto, debated the benefits of screening all men for prostate cancer.
The dilemma of prostate cancer screening is 2-pronged, said Dr Concato. "Is cure possible for whom it is necessary [aggressive cancers]? Is cure necessary for whom it is possible [indolent or benign cancers]?" he asked, quoting urologist Willet Whitmore.
Dr Concato argues that "we're opening up a cascade of treatment and side effects by screening people off the streets," noting that not enough morbidity and mortality is prevented to necessarily overcome the consequences of screen-detected cancers.
Presenting the flip side is Dr Fleshner, who admits that PSA is not a great screening test but says that aggressively pursuing prostate cancer does result in diminished disease-specific morbidity, and that treatments are becoming less invasive, allowing for greater preservation of sexual potency.
It was Dr Concato's own nested case-control study published last year (Arch Intern Med. 2006;166:38-43) that shaped his thinking toward PSA screening. In the study, 501 men identified as having prostate cancer who subsequently died during a 9-year follow-up were matched with 501 controls who were alive at the time their matched case patient had died. The proportion of men who received PSA screening and digital rectal examination was the same in each group, indicating no effect of screening on survival.
Despite the results of this study, some real-world issues may argue for PSA screening in some circumstances, said Dr Concato. Some patients may prefer to be screened because of a fear of cancer. In addition, the penalty for failing to diagnose a cancer can be severe, whereas the reward for treatment is potentially high.
Rather than encouraging screening, physicians should "acknowledge uncertainty and obtain verbal informed consent to the test," he said.
The benefits of early intervention are too great to ignore screening, countered Dr Fleshner, adding that case-control studies of 7 to 10 years' duration are too short to observe the benefit of treatment, which is apparent for early-stage cancers.
Although the true sensitivity of PSA screening is unknown, and its positive predictive value is only about 50%, more than 90% of PSA-detected cancers fit the criteria for aggressive cancers, defined as a Gleason score of ≥7, said Dr Fleshner.
Admittedly, the PSA test isn't a great screening tool, Dr Fleshner said, but it has prompted an increase in prostate biopsies, which isn't necessarily bad. "PSA has clinical utility but for the wrong reason," he said. "It has given us an excuse to put a needle in the prostate. For those with low-grade disease, we advocate watchful waiting to see what happens; but for patients with intermediate- or high-grade disease, we recommend therapy. Unless you do a biopsy, you don't know what category you're in. So the PSA test is a reason to do a biopsy. If you want to find people to cure, you have to find it [the cancer]."
Treatment of early-stage cancer is effective in reducing disease-specific mortality, he said. The Scandinavian Prostate Cancer Study Group (N Engl J Med. 2002;347:781-789) found a 50% reduction in death from prostate cancer among men with early prostate cancer who had surgery as opposed to watchful waiting, and a 37% reduction in the risk of metastatic disease, although overall mortality was unaffected during the 6.2 years of follow-up.
Minimally invasive ablative treatments that are now around the corner will have minimal impact on sexual function, he predicts, making treatment options more acceptable.
Taking the patient's age and life expectancy into consideration will focus screening on those most likely to benefit from treatment, said Dr Fleshner. "If I was 65 and diagnosed with low-core disease, I would shake my doctor's hand and say 'Thanks for the good news,'" he said. "You have to look at your patient and ask, 'Is this someone in whom I want to make a diagnosis of early-stage prostate cancer?'"
Dr Concato insisted that the limited efficacy of PSA testing in prolonging survival should be explained to patients during the process of obtaining their informed consent.