Abstract A74: A dichotomy between the risk and histology in bladder cancer among blacks and whites: An epidemiological study

Abstract

Abstract Background: Urinary bladder cancer, despite being the second most common genitourinary disease in the U.S. still presents a number of as yet unsolved complexities. Known to much of the literature is the 2:1 trend of the White to Black cancer rate, the three main histological types of bladder cancer – transitional cell carcinomas (90%), squamous cell carcinomas (5%), and adenocarcinomas (2%), and that smoking is the main etiologic factor contributing to bladder cancer. Historically, Blacks have been identified as having higher smoking rates than Whites. Therefore, the racial discrepancy in bladder cancer rates remains to be explored at the cellular level in light of the contrasting trend in smoking rates. Objective: To demonstrate that higher transitional cell carcinoma (TCC) incidences prevail in the bladder in Whites compared with Blacks, even though Blacks have a higher rate of smoking than Whites. Methods: The National Cancer Institute's SEER*stat program version 7.0.4 was used to collect bladder cancer rates for each histological type by age, sex, race, U.S. county, and year of diagnosis. Additionally, lung cancer rates, used as a surrogate for smoking, by county and overall case-specific data were obtained. SAS 9.1 and Microsoft Excel were used to analyze the data in the production of trend, frequency-density, and log-linear plots, correlation analyses, and linear regressions. Results: The 1973–2008 age-adjusted incidence of TCC of the bladder among Blacks and Whites was 11 and 21 cases per 100,000 persons respectively. Similarly, Black and White rates for TCCs of the renal pelvis were 0.54 and 0.95 cases per 100,000 persons and were 0.21 and 0.61 cases per 100,000 persons for TCCs of the ureter. However, in contrast, lung cancer rates for Blacks and Whites were 82 and 64 cases per 100,000 persons respectively. Frequency-density plots revealed similarity in curves among Blacks and Whites, peaking once between the ages of 65 and 80 years and showing bell-shaped distribution. Bivariate correlation analysis indicated that bladder and lung cancer rates were significantly correlated at about 77%. A statistically significant linear model (R2=0.75) regressing bladder cancer rates on age group, race, sex, and lung cancer rates, was evaluated and revealed that in a population that does not smoke, there were 105 White and 47 Black cases per 100,000 persons on average. Conclusions: Regardless of higher smoking rates in Blacks than in Whites, Whites have higher rates of TCCs of the bladder as well as of other sites including the renal pelvis and ureter. Even in a population considered without smoking, the trend persists with Whites having higher incidences of bladder cancer than Blacks. Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A74.