Cholecystectomy and the incidence of breast cancer: a cohort study.

A cohort comprising 11678 women who had undergone cholecystectomy in the period 1964 through 1967 for a benign gallbladder disease was investigated. They represented almost a total ascertainment from a defined geographic area. Follow-up during 11-14 completed years of observation revealed a total of 202 breast cancer cases after the cholecystectomy. This number was close to the expected incidence of 199.1 (relative risk 1.0). Further analysis of the risk in relation to duration of observation and age at operation did not reveal any trend or subgroup with a significantly increased or decreased risk. It was concluded that despite the many epidemiologic observations indicating that in Western Countries dietary habits are particularly important determinants of the high incidence of both gallstone disease and breast cancer, our results contradict the idea that the diseases share common aetiologic factors.