Multiple primary cancers following exposure to benzidine and beta-naphthylamine.

The incidence of second primary cancers has been ascertained in 3,322 employees who had worked from 1950 to 1978 in industries in Japan that manufactured benzidine and beta-naphthylamine. Of the 244 workers who had suffered from and died of cancer of the genitourinary organs (first primary cancer), 11 (all male) had subsequent primary, histologically confirmed cancers of the liver, gallbladder, bile duct, large intestine, and lung. A control group of 177 male bladder cancer patients, assembled from the Osaka Cancer Registry during 1965-1975, showed eight cases of a second primary, five being stomach cancer. No stomach cancer was observed in the study cohort. A statistically significant excess risk for liver, gall bladder, and bile duct cancer (p less than 0.05) was found The number of observed deaths from respiratory cancer was greater than expected, though not statistically significant. These findings appear to confirm previous clinical data suggesting an increased occurrence of multiple primary cancers in workers exposed to benzidine/beta-naphthylamine, pointing to a pluripotential action of these carcinogens.