Objective: To determine the extent to which the year of diagnosis, year of birth, and age at diagnosis influence the incidence trends of kidney cancer in the United States. Methods: Cancer registry data from the National Cancer Institute's Surveillance, Epidemiology, and End-Results (SEER) program were obtained for 64,041 patients with kidney cancer diagnosed between 1973 and 2008. Overall and age-specific incidence rates were calculated and adjustments were made for birth cohort and period effects. Results were stratified by race and sex. Age-period-cohort analysis was used to examine the effects of age, year of diagnosis (period), and year of birth (cohort) on incidence trends. Results: The overall age-standardized annual incidence per 100,000 increased during the study period (1973 to 2008) by race, from 6.75 (95% confidence interval, 6.18-7.36) to 19.56 (18.85-20.20) among whites, from 5.31 (3.50-7.71) to 25.38 (23.00-27.92) among blacks, and from 5.61 (3.50-8.50) to 13.98 (12.41-15.71) among other races; and by sex, from 9.44 (8.49-10.47) to 26.48 (25.39-27.60) among men and from 4.21 (3.65-4.84) to 13.38 (12.64-14.11) among women. Age-period-cohort analysis revealed a strong influence from period and cohort effects. The 1983 birth cohort, for example, had a 2-fold increase in kidney cancer (incidence rate ratio, 1.93 [1.63-2.25]) compared with the referent 1948 cohort. Conclusion: From 1973 to 2008, the incidence rate of kidney cancer increased for each sex and race across all age groups. Age-period-cohort models revealed that period-related factors, although significant, cannot alone account for these unfavorable temporal trends.
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