Breast-conserving surgery with or without irradiation in women with invasive ductal carcinoma of the breast receiving preoperative systemic therapy: A cohort study

PURPOSE: To investigate the outcomes of adjuvant whole breast radiation therapy (WBRT) in patients with invasive ductal carcinoma of the breast (breast IDC) receiving preoperative systemic therapy (PST) and breast-conserving surgery (BCS), and their prognostic factors, considering overall survival (OS), locoregional recurrence (LRR), distant metastasis (DM), and disease-free survival. PATIENTS AND METHODS: Patients diagnosed as having breast IDC and receiving PST followed by BCS were recruited and categorized by treatment into non-breast radiation therapy [BRT] (control) and WBRT (case) groups, respectively. Cox regression analysis was used to calculate hazard ratios (HRs) and confidence intervals (CIs). RESULTS: Multivariate Cox regression analyses indicated that non-BRT, cN3, and pathologic residual tumor (ypT2–4) or nodal (ypN2–3) stages were poor prognostic factors for OS. The adjusted HRs (aHRs; 95% CIs) of the WBRT group to non-BRT group for all-cause mortality were 0.14 (0.03–0.81), 0.32 (0.16–0.64), 0.43 (0.23–0.79), 0.23 (0.13–0.42), 0.52 (0.20–1.33), and 0.34 (0.13–0.87) in the ypT0, ypT1, ypT2–4, ypN0, ypN1, and ypN2–3 stages, respectively. The aHRs (95% CIs) of the WBRT group to non-BRT group for all-cause mortality were 0.09 (0.00–4.07), 0.46 (0.26–0.83), 0.18 (0.06–0.51), 0.28 (0.06–1.34), 0.25 (0.10–0.63), 0.47 (0.23–0.88), and 0.32 in the cT0–1, cT2, cT3, cT4, cN0, cN1, and cN2–3 stages, respectively. The WBRT group exhibited significantly better LRR-free and DM-free survival than the non-BRT group, regardless of the clinical T or N stage or pathologic response after PST. CONCLUSION: WBRT might lead to superior OS and LRR-free and DM-free survival compared with the non-BRT group, regardless of the initial clinical TN stage or pathologic response.