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This review aims to summarize and assess key studies investigating the relationship between hormonal contraception and breast cancer risk. Approximately two-thirds of breast cancers express the estrogen receptor, and long-term exposure to estrogen is a debated risk factor for breast cancer development. This hypothesis is based on prior studies looking at reproductive risk factors (endogenous estrogen exposure) along with hormone replacement therapy (exogenous hormone exposure). Historically accepted reproductive risk factors include age at menarche, age at first delivery, and parity. Exogenous hormone exposure encompasses both receipt of hormonal contraception and menopausal hormone replacement therapy. This review highlights the reported risks associated with the most common hormonal contraception methods including oral, transdermal, and transvaginal routes. Large observational studies of the past and more recent works are summarized highlighting gaps in knowledge. Several themes emerge: difficulty accounting for well-established risk factors in analyses of epidemiologic studies, challenges determining whether associations between hormonal contraception and breast cancer are due to the exogenous hormones themselves or to increased engagement with the medical system, and discrepancies between statistically significant and clinically significant risk, odds, and hazard ratios. Understanding the strengths and limitations of these studies will help providers in and outside of oncology support women making decisions regarding both cancer risk-reduction and family planning.
RESUMO
INTRODUCTION: The rate of mastectomy in lumpectomy-eligible patients with unilateral breast cancer is increasing. We sought to investigate the association between magnetic resonance imaging (MRI) and surgical management of patients with early-stage breast cancer by comparing the rate of mastectomy as first surgery in patients with and without preoperative MRI. METHODS: A bi-institutional retrospective study included patients diagnosed between 2016 and 2020. Lumpectomy-eligible patients with in situ and invasive cancer were included. Those receiving preoperative therapy, MRI before diagnosis, or with known bilateral cancer were excluded. The risk factors for bilateral and multicentric disease were accounted for. Fisher's exact and chi-square tests compared categorical variables, Wilcoxon two-sample test analyzed continuous variables, and multivariate analyses were performed with Poisson regression. RESULTS: Four hundred twenty-eight participants met inclusion criteria. Patients who received MRI were younger (58 versus 67 y; P < 0.001) and had denser breasts (group 3 or 4; 61% versus 25%; P < 0.001). Mastectomy rate was twice as high in patients undergoing MRI (32% versus 15%, rate ratio 2.16; P < 0.001), which remained significant in multivariate analysis (rate ratio 2.0; P < 0.001). Contralateral mastectomy (12% versus 4%; P = 0.466) and reexcision (13% versus 12%; P = 0.519) rates were similar. Time to surgery was greater in those receiving MRI alone and MRI biopsy (34 [no MRI] versus 45 [MRI] versus 62 [MRI biopsy]; P < 0.001 for both). CONCLUSIONS: MRI receipt is associated with a doubled rate of mastectomy in lumpectomy-eligible patients. Future work is needed to standardize patient selection for MRI to those with the highest likelihood of having additional undiagnosed disease.
