Cancer of the urinary bladder in blacks and whites. A case-control study.

Racial differences in the risk of cancer of the urinary bladder associated with cigarette smoking and alcohol consumption were examined in a study of 1663 cases (1534 whites and 129 blacks) and 4930 controls matched 3:1 by sex, race, and age to the cases. Significant increases in cancer risk associated with cigarette smoking were observed in whites and blacks; however, the dose-response patterns appeared to differ by race. In whites, statistically significant elevations of threefold and higher were observed in the odds ratios at all smoking levels above 20 pack-years, whereas in blacks, the corresponding point estimates did not increase significantly until greater than 60 pack-years of smoking. Although these risk patterns are compatible with the higher incidence of bladder cancer in white men, the sample of blacks was small, and tests of significance were only suggestive of higher risks for whites at specific amounts of smoking (P less than 0.15). Effects of alcohol consumption were inconsistent, and there was no detectable synergism between smoking and drinking. Additional study of race-specific risk factors and tobacco metabolism will be needed to determine the true nature of the apparent racial differences in the risk of urinary bladder cancer associated with cigarette smoking.