Regular drug use and cancer

An extensive survey study of 25,000 patients admitted to 24 Boston-area hospitals during the first 10 months of 1972 provided data which were used to estimate the proportion of cancer that is likely to be due to recent regular intake of drugs normally used to treat illness. Cancer was diagnosed for the first time in some 800 patients. The regular drug use before admissions among these patients was compared to that of 3,443 non-cancer patients admitted for conditions thought to be unrelated to any regular drug use. Controlling for age and sex, the risk ratio point estimate for any regular drug use among cancer patients was 0.88 when compared to that of reference patients. The 90% upper confidence bound was 1.02. These data indicate with 90% confidence that less than 1% of the cancers identified in this study were likely to have been caused by any recent regular use of drugs.