Overdiagnosis Due to Prostate-Specific Antigen Screening: Lessons From U.S. Prostate Cancer Incidence Trends

Etzioni R, Penson DF, Legler JM, et al. J Natl Cancer Inst. 2002; 94:981-990.

Abstr Hematol Oncol. 2002;5(4) 

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Editorial Comment: Study Sheds Light on the Problem of Screening-Associated Overdiagnosis of Prostate Cancer

Peter R. Carroll, MD

Because the incidence of prostate cancer in the United States is high, its detection and treatment are of major importance. However, there is uncertainty about the benefits of early detection, and there is no consensus about what constitutes the best treatment of any stage of the disease. It is well-known that small, latent cancers are commonly identified in autopsy studies of men whose deaths were attributed to other diseases. Currently, prostate cancer is largely detected through the use of serum prostate-specific antigen (PSA) testing.[1] Such testing may detect some cancers that would not have become apparent during a person's lifetime. Such detection has been termed "overdiagnosis."

Prostate cancer may have a protracted natural history and, in some patients, may never be associated with mortality or morbidity even if untreated. This is an important issue, because treatment can be associated with significant side effects. Although randomized trials of early detection are ongoing, the results will not be available for some time.

The authors of the current study developed a unique model of PSA testing and subsequent prostate cancer diagnosis and all-cause mortality allowing them to determine the proportion of patients whose cancer was detected through PSA testing but did not survive long enough for the cancer to be detected clinically. Overdiagnosis rates of 29% and 44% were noted for white and black men, respectively. Using such information, it appears that few latent prostate cancers are detected by PSA testing (15% and 37% of latent cancers in white and black men, respectively).

The study has limitations. The data were restricted to older men, and no information was given on what prompted PSA testing. However, the study supports the notion that a small but significant number of prostate cancers currently detected may not require immediate, aggressive therapy. The challenge is to determine which cancers currently detected are indolent. Current data suggest that reliance on cancer grade, T stage, serum PSA, and patient age and comorbidity may be helpful in this regard. Patients thought to be at low risk for immediate progression (ie, low-grade, low-volume, and organ-confined cancers associated with low serum PSA values) may be candidates for active surveillance with deferred treatment if they show clinical evidence of cancer progression over time. In fact, preliminary clinical reports suggest that most of these patients do not progress.[2,3] Obviously, further follow-up and evaluation is needed. Patients must also be reminded that no risk assessment scheme is entirely accurate and further research is needed to determine if novel phenotypic or genetic markers can do better than current techniques in this regard.[4]


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