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Prostate Cancer: To Screen or Not to Screen
Am Fam Physician. 2009 Dec 1;80(11):1294-1297.
Background: Prostate cancer screening recommendations vary widely because of unclear benefits in reducing morbidity or mortality. The American Urological Association and the American Cancer Society recommend annual prostate-specific antigen (PSA) testing and digital rectal examination (DRE) beginning at 50 years of age, with earlier testing for high-risk subgroups. The U.S. Preventive Services Task Force (USPSTF) does not recommend for or against screening in men younger than 75 years, and recommends against screening men who are older than 75 years. The Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial is an ongoing randomized controlled trial assessing the benefits of cancer screening. Andriole and colleagues recently released their interim findings regarding prostate cancer screening at the recommendation of the trial's supervisory board.
The Study: The trial coordinators recruited 76,693 men 55 to 74 years of age with no history of prostate cancer or recurrent cancer treatment. Screening group participants (n = 38,343) were offered annual DRE and PSA testing, with PSA levels greater than 4.0 ng per mL (4.0 mcg per L) or suspicious DRE findings triggering further evaluation. The control group (n = 38,350) was not offered screening, but they could still receive it as part of their regular medical care. The primary end point was death from prostate cancer. Seven-year follow-up data were available for 98 percent of participants, and 10-year follow-up data were available for 67 percent of participants.
Results: In the screening group, 85 percent of men received PSA testing and 86 percent received DRE, compared with 52 and 46 percent, respectively, in the control group. After seven years, prostate cancer was diagnosed 22 percent more often in the screening group, with similar rates of diagnosis at 10 years. Most cancers in both groups were stage II at diagnosis and were primarily adenocarcinomas. Stage III or IV prostate cancer rates were similar between groups, although the control group was more likely to have Gleason scores of 8 to 10, reflecting more aggressive disease (11.5 versus 8.4 percent, respectively). Frequency and types of treatment (i.e., resection, irradiation, and hormone therapy) were similar in both groups.
No significant difference in prostate cancer mortality (overall or by tumor stage) occurred between groups at seven and 10 years. Death rates were also unaffected by the number of PSA tests performed (i.e., only one PSA test versus two or more tests).
Conclusion: At seven years of follow-up, regular prostate cancer screening was associated with a 22 percent greater rate of prostate cancer diagnosis, but with no reduction in prostate cancer mortality. These findings support the recommendations of the USPSTF for prostate cancer screening, especially against screening all men older than 75 years.
Andriole GL, et al. Mortality results from a randomized prostate-cancer screening trial [published correction appears in N Engl J Med. April 23, 2009;360(17):1797]. N Engl J Med. March 26, 2009;360(13):1310–1319.
editor's note: Although this trial has failed to show a clinical benefit of prostate cancer screening, the debate will continue for several reasons. Prostate cancer is slow growing—despite the early release of these data, the prostate arm of the PLCO trial will continue until at least 13 years of data are accumulated for a more conclusive report of the benefits of screening. Because the control group also had high rates of prostate cancer screening (46 percent), this may have masked its benefits in the actual screening group. Furthermore, some advocates of testing argue that a PSA value of 4.0 ng per mL is too generous, and may miss many treatable prostate cancers. According to an interim report from the ongoing European Randomized Study of Screening for Prostate Cancer (ERSPC), evaluating PSA levels greater than 3.0 ng per mL (3.0 mcg per L) may reduce prostate cancer by 20 percent over nearly nine years of follow-up; however, this came at a high risk of overdiagnosis (with up to one half of identified men being asymptomatic during their lifetime) and overtreatment (1,410 men needing to be screened, and 48 cases of prostate cancer requiring treatment to prevent one death from prostate cancer).1
The PLCO and ERSPC studies are ongoing, and final results will not be available for nearly a decade. However, the PLCO's current findings support the USPSTF's recommendations to avoid routine screening in all men older than 75 years, and this can be useful in discussions with our patients.—k.t.m.
1. Schröder FH, Hugosson J, Roobol MJ, et al. Screening and prostate-cancer mortality in a randomized European study. N Engl J Med. 2009;360(13):1320–1328.
Copyright © 2009 by the American Academy of Family Physicians.
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