Mastectomy Without Radiation Therapy Had Inferior Outcomes As Compared to Breast Conserving Surgery or Mastectomy Plus Radiation Therapy in Patients with T1-2N1 Triple-Negative Breast Cancer: Analysis of 412 Patients in a Single Institution

Abstract

To compare the treatment outcomes of breast conserving surgery plus radiotherapy (BCS+RT) vs. mastectomy plus radiotherapy (mastectomy+RT) vs. mastectomy without radiotherapy (mastectomy alone) for patients with pT1-2N1 triple negative breast cancer (TNBC). A total of 412 patients with pT1-2N1 TNBC treated between 1999 and 2013 were analyzed. Patients underwent BCS+RT (n=48) or mastectomy+RT (n=103) or mastectomy alone (n=261). No neoadjuvant chemotherapy was used and axillary dissection was performed for all patients. All received adjuvant chemotherapy, mainly anthrathycline- and/or taxane-based regimens. The Locoregional recurrence (LRR), disease-free survival (DFS) and overall survival (OS) rates were calculated by the Kaplan-Meier method and compared with log-rank test. Multivariate analysis was performed by Cox model. The median follow-up time was 61 months.The median age was 49 years (range, 21-82). The median nubmer of positive axillary nodes was 1 (range, 1-3) and the median number of nodes dissected was 19. BCT+RT group and mastectomy+RT group had more patients with age < 50 years than mastectomy alone group (68.8% vs. 63.1% vs. 46.0%, p < 0.001). mastectomy+RT group had more patients with 2-3 positive nodes than BCT+RT group and mastectomy alone group (63.1% vs. 41.7% vs. 41.4%, p = 0.001). BCT+RT group had more T1 tumors than mastectomy+RT group and mastectomy alone group (64.5% vs. 31.1% vs. 44.4%, p < 0.001). mastectomy+RT group had more T2 tumors than mastectomy alone group (68.9% vs. 55.6%, p = 0.019). Among BCT+RT group, mastectomy+RT group and mastectomy alone group, the 5-year LRR rates were 2.4% vs. 6.2% vs. 12.8% (p=0.180), the 5-year DFS rates were 90.4% vs. 85.7% vs. 72.7% (p=0.038), the 5-year OS rates were 91.6% vs. 89.4% vs. 85.6% (p=0.098). There were no significant differences in DFS and OS between BCT+RT group and mastectomy+RT group (p=0.267, p=0.814), however mastectomy only group had lower DFS and OS than matectomy+RT group (p=0.034, p=0.082). Multivariate analysis showed similar results after adjusting for covariates: there were no significant differences in LRR, DFS and OS between BCT+RT group and mastectomy+RT group; mastectomy alone was independently associated with higher LRR (p=0.008, HR:2.86) and lower DFS and OS (p=0.002, HR:2.08; and p=0.009, HR:2.35) as compared with BCT or mastectomy plus RT. T2 tumors was independent unfavorable prognostic factor for LRR, DFS and OS (p=0.026, p=0.002, p=0.010, respectively). In addition, age < 50 years (p=0.017) and 2-3 positive nodes (p=0.019) were independent unfavorable prognostic factor for LRR. In pT1-2N1 TNBC, breast conserving surgery plus RT achieved comparable outcomes with mastectomy plus RT, but mastectomy without RT had poorer outcomes. This indicates that breast conserving therapy is safe and postmastecomy RT is recommended for all patients.