Operable Breast Cancer of the Inner Hemisphere Is Associated with Poor Survival

PURPOSE: This study investigated the clinicopathological features of operable breast cancer lesions located in different hemispheres of the breast and determined related survival outcomes. METHODS: Data from 5,330 patients with invasive ductal carcinoma were retrospectively analyzed based on tumor location. RESULTS: The median follow-up time was 68 months (range, 18-176 months). Patients with breast cancer located in the outer hemisphere of the breast had lesions with more advanced nodal stages and more frequently received adjuvant chemotherapy than patients with breast cancer in the inner hemisphere. The 5-year disease-free survival (DFS) rates of patients with tumors located in outer versus inner hemispheres were 81.5% and 77.0%, respectively (p=0.004); the overall survival (OS) rates were 90.7% and 88.8%, respectively (p<0.001). The association between tumor location and the 5-year DFS rate was most apparent in node-positive patients (73.1% vs. 65.8% for outer vs. inner hemisphere lesions, p<0.001) and in patients with primary tumors greater than 2 cm in diameter (78.2% vs. 72.3%, p=0.002). Multivariate analysis showed that tumor location was an independent predictor of DFS (hazard ratio [HR], 1.23; p=0.002) and OS (HR, 1.28; p=0.006). There were no significant differences in 5-year DFS or OS rates between patients with outer versus inner hemisphere tumors when internal mammary node irradiation was performed. CONCLUSION: This study demonstrated that tumor location was an independent prognostic factor for operable breast cancer. Internal mammary node irradiation is recommended for patients with breast cancer of the inner hemisphere and positive axillary lymph nodes or large primary tumors.