Population based analysis of the increasing incidence of kidney cancer in the United States: evaluation of age specific trends from 1975 to 2006.

PURPOSE: An increase in kidney cancer was reported in the United States but overall rates may obscure trends in age specific groups. We explored whether the increase in kidney cancer incidence differs across age groups.
MATERIALS AND METHODS: We ascertained the 63,843 incident renal cancer cases in SEER (Surveillance, Epidemiology and End Results) cancer registries for 1975 to 2006. Yearly incidence rates of renal cancer were calculated and stratified by age group. Age specific trends in cancer diagnosis were evaluated by Poisson regression.
RESULTS: From 1975 to 2006 the overall age adjusted renal cancer incidence increased 238% from 7.4/100,000 to 17.6/100,000 adults. From 1991 to 2006 the mean age at diagnosis decreased from 64.7 to 62.7 years and the proportion of patients diagnosed before age 65 years increased from 45.9% to 55.3%. Age specific incidence rates of renal cancer increased in all age groups from 1975 to 2006 (p <0.0001). However, the rates changed at different rates. Overall renal cancer diagnosis in the youngest age group (20 to 39 years) increased more quickly than all other age groups (p <0.0001). The renal cancer incidence in patients 60 to 69 and 70 to 79 years old increased more rapidly than in those 40 to 49 and 50 to 59 years old (p <0.01).
CONCLUSIONS: In the last 15 years mean age at diagnosis of renal cancer has decreased. During our study period the most rapidly increasing kidney cancer incidence was seen in those younger than 40 and 60 to 79 years old. The renal cancer increase in younger patients should direct attention toward further evaluation of renal cancer risk factors.