Progestagens use before menopause and breast cancer risk according to histology and hormone receptors.

In a previous study, we found a positive association between premenopausal use of progestagens and breast cancer risk. We conducted the present study to assess the risk of breast cancers defined by their histology and hormone receptors status. We evaluated the association between progestagen-only intake (except for mini pills) before menopause and after the age of 40 years and invasive breast cancer risk in 67,057 women participating in the French E3N cohort study. Histologically confirmed invasive breast cancers (2,264) were identified through biennial self-administered questionnaires completed from 1992 to 2002. Risk estimates were calculated using the Cox proportional hazard model. We found an increased risk of lobular carcinoma associated with premenopausal use of progestagens among both current and past users [hazard ratio (HR), 1.51; 95% confidence interval (95% CI), 1.02-2.24 and HR, 1.38; 95% CI, 1.08-1.75, respectively]. Among current users, the use of progestagens for 4.5 years or more was associated with an increased risk of estrogen receptor-positive/progesterone receptor-positive carcinomas (HR, 1.68; 95% CI, 1.05-2.68), whereas current use of progestagens for <4.5 years was associated with an increase in the estrogen receptor-positive/progesterone receptor-negative carcinoma risk (HR, 1.61; 95% CI, 1.05-2.46). The premenopausal use of progestagens after the age of 40 years may be preferentially associated with the risk of lobular breast cancer and differentially affect the risk of breast cancer according to the hormone receptor status.