Cyclical mastalgia and breast cancer risk: results of a French cohort study.

Cyclical mastalgia is a common complaint, with a potentially important relationship to breast cancer risk. In the last decade, case-control studies have reported that cyclical mastalgia could be considered as an independent risk factor for breast cancer. The subjectivity of a retrospectively collected symptom questioned the validity of this finding. We have examined the association between cyclical mastalgia and breast cancer risk in the French cohort study of women with benign breast disease diagnosed in two breast clinics between 1976 and 1979 and followed-up until 1997. The present study was restricted to the women free of any hormonal treatment (n = 247). The mean follow-up was 16 +/- 5 years, and a total of 22 breast cancers occurred during the follow-up. Using a Cox model with duration of cyclical mastalgia as a time-varying variable, the adjusted relative risk of breast cancer increased with the duration of cyclical mastalgia (P = 0.006). The corresponding relative risk for 37 months of cyclical mastalgia was 5.31 (95% confidence interval, 1.92-14.72). We show here that the conclusion still holds when the symptom cyclical mastalgia was collected prospectively in a cohort study, bringing additional evidence that cyclical mastalgia may represent an independent and useful clinical marker of increased breast cancer risk. It might be a confounding factor when assessing the effects of hormonal treatments on breast cancer risk such as hormonal replacement therapy or oral contraceptives.