Trends in Stage-Specific Incidence Rates for Urothelial Carcinoma of the Bladder in the United States: 1988 to 2006

BACKGROUNDBladder cancer is notable for a striking heterogeneity of disease-specific risks. Among the approximately 75% of incident cases found to be superficial to the muscularis propria at the time of presentation (non-muscle-invasive bladder cancer), the risk of progression to the lethal phenotype of muscle-invasive disease is strongly associated with stage and grade of disease. Given the suggestion of an increasing percentage of low-risk cases in hospital-based registry data in recent years, the authors hypothesized that population-based data may reveal changes in the stage distribution of early-stage cases. METHODSSurveillance, Epidemiology, and End Results (SEER) data were used to examine trends for the stage-specific incidence of bladder cancer between 1988 and 2006, adjusted for age, race, and sex, using Joinpoint and nonparametric tests. RESULTSThe adjusted incidence rate of papillary noninvasive (Ta) predominantly low grade (77%) disease was found to increase from 5.52 to 9.09 per 100,000 population (P<.0001), with an average annual percentage change of +3.3. Over the same period, concomitant, albeit smaller, decreases were observed for flat in situ (Tis) and lamina propria-invasive (T1) disease (2.57 to 1.19 and 6.65 to 4.61 per 100,000 population [both P<.0001]; average annual percent change of -5.0 and -1.6, respectively). The trend was most dramatic among patients in the oldest age strata, suggesting a previously unappreciated cohort phenomenon. CONCLUSIONSThe findings of the current study should motivate further epidemiological investigations of differential associations of genetic and environmental factors with different bladder cancer phenotypes as well as further scrutiny of clinical practice guideline recommendations for the growing subgroup of predominantly older patients with lower-risk disease. Cancer 2014;120:86-95. (c) 2013 American Cancer Society. The authors observed what to their knowledge is a previously unappreciated increase in adjusted incidence rates of low-risk, papillary noninvasive (Ta) bladder cancer, the overwhelming majority of which was low grade, in the United States from 1988 through 2006. The trend appears to be driven in large part by dramatic increases in the incidence of Ta disease among the oldest age strata, suggesting a cohort phenomenon warranting further investigation given the differential molecular biology of low-grade versus high-grade urothelial carcinoma.