to the editor: I read with great interest Dr. LeFevre's article, “Prostate Cancer Screening: More Harm Than Good?”1
in the August 1998 issue of American Family Physician
. Dr. LeFevre provided a great overview of the general principles of prostate cancer screening. He pointed out that the tests currently available for prostate cancer screening do not meet the criteria to justify mass screening because the data suggest that screening often detects what may be indolent, nonaggressive prostate cancer. The data also suggest that the treatment of such a cancer with radiation or prostatectomy could result in significant morbidity without a proven decrease in mortality.
Unfortunately, Dr. LeFevre neglected the data that black men and white men do not have equal stage-specific rates of survival when adjusted death rate ratios are computed.2
Compared with whites, blacks have a poorer rate of prostate cancer survival.3
This finding is most consistent with the hypothesis of increased tumor virulence in blacks.2
Blacks have higher incidence rates for prostate cancer than do whites at every age-specific interval.4
Although the rate of mortality related to prostate cancer has decreased in both whites and blacks, it is much higher in blacks than in whites among younger age groups, when the prevalence of prostate cancer is relatively low. As a result, fewer blacks with prostate cancer survive to older ages.4
Over the past decade, blacks have shown a decline in tumor cells burden at the time of diagnosis as reflected by a decline in the mean levels of prostate-specific antigen.5
Current diagnostic trends toward the persistent, increased detection of localized prostate carcinoma in younger men, combined with a marked reduction in the distant stage disease, suggest significant potential reductions in mortality.6
These trends have much greater implications for blacks.
More research and continued prostate cancer screening are needed, with a special emphasis on risk groups for whom current screening tests would have a significant yield.
in reply: Dr. Bowden accurately highlights racial differences in prostate cancer incidence and mortality. Indeed, the screening study cited in my article1
demonstrated a higher incidence of prostate cancer in black men than in white men, as well as a greater likelihood for distant spread at the time of diagnosis. I agree with Dr. Bowden's statement that the literature is consistent with the hypothesis of increased tumor virulence in blacks.
What are the implications of these data for prostate cancer screening? Blacks stand to gain more than whites from an effective screening program that truly detects aggressive disease at a stage in which curative therapy is possible and with treatment that does not have a significant probability of morbidity and mortality. To the extent that treatment does cause morbidity and mortality, and screening detects disease for which therapy does not significantly alter the natural history, then blacks also have more to lose than whites. I don't find a decline in PSA levels at the time of diagnosis to be compelling evidence of the efficacy of screening.
Ongoing randomized trials of screening and treatment for prostate cancer will provide important data; it is imperative that we be able to stratify by race in such studies, given the discrepancies noted by Dr. Bowden. Without significant changes in treatment, a dramatic drop in death rates from prostate cancer in the United States would also be highly suggestive evidence that screening is effective. Similar data ultimately demonstrated the efficacy of Papanicolaou smear screening in the prevention of deaths related to cervical cancer. Unfortunately, it is likely that meaningful answers regarding prostate cancer screening are five to 10 years away. Until then, an honest portrayal of the limitations of existing information is necessary for truly informed choice.