Trends in the incidence of testicular germ cell tumors in the United States

BACKGROUND. Recent reports have suggested that the increasing rates of testicular germ cell tumors in some populations have begun to plateau. This study was conducted to examine whether rates among white men in the United States have begun to stabilize and whether rates among black men in the United States have remained low. METHODS. Testicular germ cell tumor incidence data from in the Surveillance, Epidemiology, and End Results Program were analyzed for the years 1973-1998. Trends were examined separately for seminoma and nonseminoma. Using age-period-cohort analyses with 5-year age intervals and 5-year calendar-period intervals, changes in the slope of the trends in birth-cohort and calendar-period effects were examined. RESULTS. Among white men, rates of seminoma continued to increase, but the rate of increase steadily declined throughout the 26-year time span. Nonseminoma rates among whites increased more slowly during the first three time intervals, then plateaued in the final interval. Rates of both seminoma and nonseminoma in black men fluctuated throughout the first three time intervals. In the final interval, the rates of seminoma increased almost 100%, whereas the rates of nonseminoma increased more modestly. Age-period-cohort modeling of the incidence data in white men found that, whereas the dominant effect was that of birth cohort, there also was a period effect. CONCLUSIONS. Among white men in the United States, the incidence of testicular germ cell tumors varied by histology, with a continuing increase in risk only for seminoma. Among black men in the United States, the surprising increases seen between 1988 and 1998 were likely to be a calendar-period effect.