Summary of First Four Prostate, Lung, Colorectal, and Ovarian Screening Roundsa continued...
Prostate biopsies in a small percentage of men will demonstrate prostatic intraepithelial neoplasia (PIN). High-grade PIN is not cancer but may predict an increased risk for prostate cancer. PSA does not appear to be elevated with PIN.[85,86]
Physician Behaviors Related to Screening
A variety of variables affect the likelihood of a recommendation for prostate cancer screening from a physician. In Washington State, 1,369 primary care physicians were surveyed to determine patterns of PSA screening recommendations. Of the 714 respondents, 68% routinely recommended PSA screening. The survey results suggest that gender (male), age (medical school graduation before 1974), and mode of reimbursement (fee for service) all increase the likelihood of PSA screening recommendations among this population.
Randomized Prospective Clinical Trials of Screening for Prostate Cancer
While two large randomized clinical trials are under way to assess whether early detection of prostate cancer can reduce mortality from the disease,[88,89] a Canadian trial has been reported to have been performed in a randomized prospective manner. In this study, 46,486 men identified from the electoral rolls of Quebec City and its metropolitan area were randomly assigned to be either approached or not approached for PSA and DRE screening. A total of 31,133 men were randomly assigned to screening, while a total of 15,353 were randomly assigned to observation. (It appears that these men were unaware that they had been enrolled in a randomized clinical trial.) A notable difference from other screening studies was that a PSA of 3.0 ng/mL was used to determine whether further evaluation was warranted. In this study (in which the patient numbers have been variously reported by the authors) of the 31,133 men who were randomly assigned to screening, 7,348 actually underwent screening while 23,785 did not. Of the 15,353 who were randomly assigned to observation, 1,122 actually underwent screening while 14,231 did not. Two hundred-seventeen deaths were noted among the 38,016 men who did not undergo screening, compared with only 11 deaths among the 8,470 men who underwent screening. Using an intention-to-treat analysis based on the study arm to which an individual was originally assigned, however, no difference in mortality was seen (there were 75 deaths among the 15,353 men who were randomly assigned to observation compared with 153 deaths among the 31,133 men randomly assigned to screening [RR, 1.085]). Because of noncompliance, this study does not answer the question of whether early detection with PSA will reduce prostate cancer mortality.
Population Observations on Early Detection, Incidence, and Prostate Cancer Mortality
While DRE has been a staple of medical practice for many decades, PSA did not come into common use until the late 1980s for the early diagnosis of prostate cancer. Following widespread dissemination of PSA testing, incidence rates rose abruptly. In a study of Medicare beneficiaries, a first-time PSA test was associated with a 4.7% likelihood of a prostate cancer diagnosis within 3 months. Subsequent tests were associated with statistically significant lower rates of prostate cancer diagnosis.