INCREASING INCIDENCE OF ALL STAGES OF KIDNEY CANCER IN THE LAST 2 DECADES IN THE UNITED STATES: AN ANALYSIS OF SURVEILLANCE, EPIDEMIOLOGY AND END RESULTS PROGRAM DATA

Abstract

Purpose: Since the 1980s with the increased use of abdominal imaging, such as computerized abdominal tomography, renal cancer has commonly been diagnosed as an incidental mass. We analyzed the renal cancer incidence from 1973 to 1998 in the Surveillance, Epidemiology and End Results program by historic staging of localized, regional or distant disease to evaluate possible stage migration due to increased abdominal imaging. Materials and Methods: We used renal cancer data from the Surveillance, Epidemiology and End Results 9 registries, public use, August 2000 submission (National Cancer Institute, Bethesda, Maryland), which represents approximately 14% of the United States population. We analyzed the age adjusted renal cancer incidence from 1973 to 1998 using the 1990 American standard million population. We compared the incidence of the 3 stages of renal cancer from 1973 to 1985 and 1986 to 1998 by the chi-square test and used joinpoint regression analysis to determine whether there was a significant change in the intragroup or intergroup incidence rate with time. Results: During 1973 to 1985 the rate of localized, regional and distant renal cancer was 45%, 23% and 32% compared with 54%, 21% and 25%, respectively, from 1986 to 1998 (p = 0.45). However, the plot of incidence rate versus diagnosis year by stage showed an increasing trend in the 3 stage groups. The annual percent change in the localized, regional and distant groups was 3.7 (95% confidence interval [CI] 3.2 to 4.2), 1.9 (95% CI 1.2 to 2.6) and 0.68 (95% CI 0.1 to 1.3) per 100,000 population, respectively (p <0.05). The 3 groups also had significantly different growth rates (p <0.01). Conclusions: There was no significant difference in stage at presentation of renal cancer diagnosed in 1973 to 1985 compared with that diagnosed in 1986 to 1998. While the lack of a decrease in distant disease despite the increased detection of regional and localized renal cancer implies that a proportion of innocuous renal cancer cases may be detected by increased abdominal imaging, the increased incidence of renal cancer in all 3 categories indicates that other factors may also be contributing to the increasing incidence of renal cancer.