Ipsilateral Breast Tumor Reappearance and Contralateral Breast Cancer after Primary Breast Cancer Treatment: A Comprehensive Retrospective Study of 15,168 Patients.

<bold>Objective:</bold> The aim of this retrospective study was to assess the risk factors for developing ipsilateral breast tumor reappearance (IBTR) and de novo contralateral breast cancer (BC) after primary BC treatment. <bold>Methods:</bold> Retrospectively, 15,168 consecutive patients with primary monolateral BC were enrolled in this monocentric study (from June 1994 to December 2006). Clinicopathological features, follow-up, and survival at 15 years were considered for statistical analysis. <bold>Results:</bold> Significant associations of increased risk for IBTR were verified with metastatic axillary lymph nodes (HR 1.37 [1.15–1.62], p = 0.0004), high tumor grade G2 (HR 1.35 [1.05–1.74], p = 0.02) and G3 (HR 1.35 [1.01–1.79], p = 0.04), luminal B (HR 1.51 [1.25–1.82], p < 0.0001), and HER2-positive (HR1.66 [1.14–2.41], p = 0.008) and triple-negative subtype (HR 1.54 [1.07–2.21], p = 0.02). Older age (HR 1.44 [1.08–1.91], p = 0.01) and positive family history (HR 1.85 [1.47–2.32], p < 0.0001) were risk factors for contralateral BC. Significant protective factors for IBTR were hormonotherapy (HR 0.71 [0.59–0.85], p = 0.0003), chemotherapy (HR 0.72 [0.60–0.87], p = 0.001), and radiotherapy (HR 0.73 [0.61–0.87], p = 0.0005). Hormonotherapy was also confirmed as a protective factor for contralateral second BC (HR 0.43 [0.30–0.60], p < 0.0001). <bold>Conclusions:</bold> We classified factors for IBTR and contralateral BC in high- and low-risk groups. In the high-risk group, breast surgery still remains more important than in the low-risk group, which seems to benefit more from adjuvant treatments. [ABSTRACT FROM AUTHOR]