Reproductive and menopausal factors and risk of second primary breast cancer after in situ breast carcinoma

摘要

PurposeIn situ breast cancer patients have a higher risk of developing a second primary breast cancer than women in the general population have of developing breast cancer. We have limited understanding of why some women with a previous in situ breast cancer develop second primary breast cancers while others do not.MethodsIn this population-based nested case-control study, we evaluated the association between reproductive and menopausal factors and risk of developing a second primary breast cancer among women with a previous in situ breast cancer. Using conditional logistic regression, these associations were evaluated in 552 cases and 1032 individually matched controls.ResultsOlder age at menarche was associated with risk of second primary breast cancer among women with a previous in situ breast cancer (compared to age12, age 13: OR 0.60 (0.42, 0.85); age14: OR 0.69 (0.47, 1.00); P-trend=0.07). Breastfeeding for 12months was associated with a decreased risk of developing a second primary breast cancer (OR 0.62 (0.39, 0.98)). No associations were observed for other reproductive or menopausal factors evaluated.ConclusionsResults from this study suggest that reproductive factors may play a role in development of a second primary breast cancer after diagnosis of in situ breast carcinoma.