Familial and environmental interactions in bladder cancer risk.

In a population-based study of 2,982 bladder cancer patients and 5,782 controls in 10 geographic areas of the United States which was designed to assess the role of environmental risk factors, information was also obtained on the history of urinary tract cancer in first-degree relatives. A family history of urinary tract cancer significantly elevated the risk of bladder cancer [relative risk (RR) = 1.45], with higher risks observed among patients under age 45. The risks of bladder cancer associated with positive family history were generally higher among persons with suspected environmental exposures, particularly heavy cigarette smoking (RR = 10.7 among those who smoked 3 or more packs per day). Further studies of bladder cancer should incorporate biochemical and genetic probes to assess mechanisms of familial susceptibility and interactions with environmental factors.