After increasing sharply from 1989 through 1992, US prostate cancer incidence rates dropped by 16% for white men and nearly stabilized for African-American men (2% increase) in the latest period available for analysis, 1992 to 1993. These findings, based on the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) cancer registry information and US Census population estimates, are reported in the November 20th issue of the Journal of the National Cancer Institute.
In this brief communication to the Journal, researcher Ray M. Merrill, phd, mph, and colleagues at the NCI explain that much of the dramatic increase in the age-adjusted prostate cancer incidence rates noted in the 1989 to 1992 period (61% among whites and 65% among African-Americans) has been attributed to the widespread use of prostate-specific antigen (PSA) for screening and detection of prostate cancer. This recent analysis of the SEER data, compiled from the 9 standard population-based tumor registries that together cover approximately 10% of the US population (with over-sampling of certain minority populations), indicates that prostate cancer incidence rates began to fall earlier in the 1992 to 1993 period in some geographic areas (eg, Seattle-Puget Sound) and that rates continue to vary by region (eg, lowest in Connecticut and Iowa; highest in metropolitan Detroit, Utah, and Seattle). (Despite these differences, the decline in incidence occurred in each SEER area.)
In addition, incidence rate changes varied by 10-year age interval and by race. For all SEER areas combined, declining rates were observed in the three older age groups for whites and the two older age groups for African-Americans. These findings are consistent with incidence trends in screened populations, say the authors. Since screening tends to identify cases earlier, incidence rates in younger age groups rise and rates in older age groups drop. Specifically, the percent changes in rates for white males from 1992 through 1993 were: +4% for ages 50 to 59 years, -9% for ages 60 to 69 years, -20% for ages 70 to 79 years, and -29% for ages 80 years and older. For African-American men, the percent changes in rates for the same time period were: +25% for ages 50 to 59 years, +15% for ages 60 to 69 years, -8% for ages 70 to 79 years, and -17% for ages 80 and older.
Merrill and his colleagues suggest that additional research is needed to determine why prostate cancer incidence rates began to decline in 1992 and 1993. The decline may, they say, reflect reduced use of PSA for screening and detection due to unresolved questions about its value, given the morbidity and mortality associated with treatment for early-stage prostate cancer. Further inquiry into the basis of the observed prostate cancer incidence rate changes may also provide additional insight into the natural history of this disease and the performance characteristics of PSA screening tests, say the researchers.