69 Background: Human Epidermal Growth Factor Receptor 2 (HER2)-positive breast cancer subtype is an adverse prognostic factor, it is unclear whether there are differences in outcomes according to the type of locoregional treatment used in this population. This study compared locoregional recurrence and survival outcomes in women with node-negative, HER2-positive breast cancer treated with Breast Conserving Therapy (BCT) versus Modified Radical Mastectomy (MRM). Methods: Independent datasets from the BC Cancer Agency (BCCA) and the Massachusetts General Hospital (MGH) were pooled and analyzed. Study subjects included 748 patients between 2003-2009 with pT1-2, N0, M0 Her2+ breast cancer, treated with BCT or MRM. Standard clinico-pathologic factors were analyzed. Kaplan-Meier locoregional recurrence (LRR), breast cancer specific survival (BCSS) and overall survival (OS) were compared between cohorts treated with BCT vs. MRM. Multivariable analysis (MVA) with Cox regression modeling was performed to evaluate the prognostic significance of type of locoregional treatment on outcomes. Results: Median follow-up time was 4.2 years for BCCA and 6.0 years for MGH. Comparison of clinico-pathologic factors according to type of locoregional treatment found that patients treated with MRM had higher proportions of grade 3 histology (69% vs. 60%, p = 0.004) and PR-negative disease (56% vs. 44%, p = 0.008) and lower rates of endocrine therapy (51% vs. 64%, p <0.001) and herceptin therapy (50% vs. 57%, p = 0.04). There were no significant differences between BCT and MRM groups in 5-year Kaplan-Meier LRR (2.0% vs. 1.7%, p=0.88), BCSS (97.2% vs. 96.1%, p=0.70), and OS (95.5% vs. 93.4%, p=0.19). On MVA, BCT and MRM were associated with similar LRR, BCSS, and OS. The only factor associated with reduced OS was T2 disease (HR 3.1, p=0.01). Conclusions: In this multi-institutional study, no significant outcome differences were found among women with T1-2 N0, HER2-positive breast cancer treated with BCT or MRM. Breast conserving therapy is safe in this population, providing high rates of locoregional control and survival equivalent to mastectomy.
Adjuvant trastuzumab reduces locoregional recurrence in women who receive breast-conservation therapy for lymph node-negative, human epidermal growth factor receptor 2-positive breast cancer
