Men enrolled in the Prostate, Lung, Colorectal and Ovarian Cancer (PLCO) Screening Trial had no evidence of a mortality benefit compared to a control group of men undergoing usual care, according to a study published online Jan. 6 in the Journal of the National Cancer Institute.
The Prostate, Lung, Colorectal and Ovarian Cancer Screening (PLCO) Trial is a multi-center, two-arm trial, which began enrollment in November 1993 with follow-up through December 2009, and was designed to evaluate the effect of screening on these specific cancers. The enrollees were aged 55-74 and had no previous personal history of these cancers. Men in the intervention arm underwent annual PSA testing for six years and annual digital rectal examination for four years, while those in the control arm received their usual medical care, which for some men included screening. A previous report of PLCO results through ten years was criticized for being too short of a follow-up period.
To determine longer-range outcomes among the men enrolled in PLCO, Gerald L. Andriole, M.D., of Washington University School of Medicine in St. Louis, and colleagues, examined outcomes of the men through 13 years. The researchers found a statistically significant 12% relative increase in the incidence rate of prostate cancer, and a non-statistically significant decrease in the incidence of high-grade prostate cancer in the intervention arm compared to the control arm, but no difference in mortality between the two arms. In addition, there was no apparent differential effect of screening by age category, pre-trial PSA testing, or co-morbidity.
The authors write, "Improvements in prostate cancer treatment are probably at least in part responsible for declining prostate cancer mortality rates. Even if life is only prolonged by therapy, the opportunities for competing causes of death increase, especially among older men."
The authors also point out that of the 4250 prostate cancer case patients diagnosed in the intervention arm, 455 (10.7%) died of causes other than the cancer types studied; in the control arm, 3815 men were diagnosed with prostate cancer of whom 377 (9.9%) died, also of other causes. "Thus, a higher percentage of deaths from other causes rather than a deficit occurred among the prostate cancer patients diagnosed in the intervention arm, an indication of the over-diagnosis associated with PSA detection," the authors write.
The researchers plan to again update the mortality findings from the prostate component of the PLCO after follow-up data through 15 years becomes available.