CSP News: Study casts doubt on value of prostate-cancer screening
From Feb. 2006 VA Research Currents (67 KB, PDF)
A VA study of about 1,000 men found no survival advantage for those who had been screened for prostate cancer. The findings appeared in the Jan. 9 Archives of Internal Medicine.
Led by John Concato, MD, MPH, and a team at Yale University and the Clinical Epidemiology Research Center and Cooperative Studies Coordinating Center at the West Haven VA Medical Center, the researchers sought to determine the effect on survival of the most common method for prostate-cancer screening: the blood test for prostate-specific antigen (PSA), with or without a digital rectal exam. Even though the PSA test can detect prostate cancer at an early stage, it has a high "false positive" rate: As many as 7 in 10 men with abnormal results find out only after further testing that they have no detectable cancer. And even for those who do receive a cancer diagnosis, the benefits conferred by early detection are questionable, say many experts.
Prostate cancer is the most common cancer and a leading cause of cancer death among American men. However, prostate cancer usually grows slowly, and many older men with the disease die of other causes before they experience any troubling symptoms from the cancer. In fact, most men develop prostate cancer if they live long enough, but fewer than 3 in 100 actually die from it. Moreover, treatment can cause serious problems, such as urinary incontinence and erectile dysfunction. H. Gilbert Welch, MD, a VA physician and health-outcomes researcher and professor at Dartmouth Medical School, wrote in the Washington Post in 2004:
"While screening probably has helped a few men live longer, it has also clearly hurt others. Millions have been biopsied who otherwise wouldn't have been. Many with non-progressive disease have been turned into cancer patients unnecessarily. Most have been treated, and many have suffered ill effects. A few have even had their lives shortened by treatment."
From nearly 72,000 older men who had received care at 10 VAMCs in New England, Concato and colleagues identified 501 men who received a diagnosis of prostate cancer between 1991 and 1995 and died by 1999. They then selected a comparison group of 501 living "control" men, with or without prostate cancer and matched to the deceased men for age and VAMC.
No benefit for screening was found, in that 14 percent of the men who died of prostate cancer and 13 percent of those in the control group had been screened with PSA. The authors reason that if PSA reduced mortality, the rate of screening among the deceased men would have been lower. Screening was also not found to reduce mortality among younger or healthier men, or when the digital rectal exam was factored in.
The authors concluded: "Optimal clinical strategies for diagnosing and treating prostate cancer remain uncertain and in need of additional investigation. Based on available evidence, including the present study, recommendations regarding screening for prostate cancer should not endorse routine testing of asymptomatic men to reduce mortality. Rather, the uncertainty of screening should be explained to patients in a process of 'verbal informed consent,' promoting informed decision making."
Concato noted in an email, "The findings are consistent with existing VA clinical recommendations regarding screening for prostate cancer."
Related VA research has focused on improving current methods of prostate-cancer detection, such as by enabling physicians to more accurately interpret screening results and risk factors; or finding new biomarkers that can be tested along with PSA to identify patients with more aggressive tumors who would undeniably benefit from treatment.