Evaluation of exogenous estrogen use in patients with lobular neoplasia and its role in subsequent breast cancer development.

BACKGROUND: There is a paucity of data regarding the impact of exogenous hormones on future breast cancer risk in the setting of lobular neoplasia. We sought to determine if patients with a history of exogenous hormone use who develop lobular neoplasia are more likely to develop future breast cancer. METHODS: Following institutional review board approval, a single-institution retrospective review was conducted of patients diagnosed with lobular carcinoma in situ or atypical lobular hyperplasia between January 2009 and December 2017. The use of exogenous hormones and future breast cancer were examined. Data were analyzed using IBM SPSS, version 29.0.2.0. RESULTS: A total of 88 patients with lobular neoplasia were identified: 57 (65%) with lobular carcinoma in situ and 31 (35%) with atypical lobular hyperplasia. At the time of lobular neoplasia diagnosis, 53 (60%) underwent surgical excision, 48 (39%) were followed in a high-risk clinic, and 13 (15%) took antiestrogen therapy for risk reduction. Fifteen patients had a history of hormone therapy use prior to lobular neoplasia diagnosis (17%), and 3 (3%) started hormone therapy following lobular neoplasia diagnosis. Median overall follow-up was 9.7 years (interquartile range, 7.2-11.4). Eleven (13%) patients developed breast cancer. Comparing those who developed breast cancer versus those who did not, there was no difference in hormone therapy use (9% vs 21%, P = .325), vaginal estrogen use (27% vs 9%, P = .110), oral contraceptive pill use (54% vs 64%, P = .675), or other hormone-based birth control (27% vs 14%, P = .402). CONCLUSION: In a single-institution cohort with long-term follow-up, the future development of breast cancer in patients diagnosed with lobular neoplasia was not associated with prior use of hormone therapy, oral contraceptive pills, vaginal estrogen, or other hormone-based birth control.