Risk Factors Of Locoregional Recurrence In Patients With N2-3a Breast Cancer Treated With Post Mastectomy Radiation

To investigate the patterns and prognostic factors of locoregional recurrence(LRR) in patients with N2-3a breast cancer after post-mastectomy radiation(PMRT). Women with breast cancer with pathologically confirmed at least 4 axillary lymph nodes metastasis treated with PMRT were extracted from our established database, which including all the breast cancer cases treated at our institution from 1999/1 to 2013/12. Patients with initially distant, internal mammary(IM) or supraclavicular(SC) lymph nodes metastasis, as well as those treated with neoadjuvant chemotherapy were excluded. We estimated survival curves using the Kaplan–Meier method, and used the log-rank test and Cox regression to determine the prognostic factors. A total of 1623 patients were included, with the median age of 48 years. The median breast tumor size was 2.5 cm. The median number of axillary positive lymph nodes was 8. ER/PR positive were seen in 75.5% of patients, Her-2 positive in 22.9% of patients, while only 9.7% patients were triple negative. All patients received radiation to the chest wall(CW) and SC. Axillary was irradiated in 200 (12.3%) patients, while only 6.7%(109) of patients underwent IM radiation. Nearly all patients received adjuvant chemotherapy. In HER-2 positive group, only 32.6%(121/371) patients received anti-HER2 therapy. While 83.3% (1021) of patients had endocrine therapy if needed. After a median follow up of 5.14 year, 26.7%(433) patients had a relapse, including 108 cases of LRR and 433 of distant metastasis. The 5-year overall survival, disease free survival and LRR free survival was 95.9%(95%CI 94.9-97.0%), 72.6%(95%CI 72.4-77.1%) and 93.6%(95%CI 92.3-95.0%), respectively. In LRR patients, 34(31.5%) cases were in the CW, 36(33.3%) in the axillary fossa, 60(55.6%) in the SC, while only 8(7.4%) cases in the IM. The 5-year recurrence rate was 1.9% in CW, 2.1% in axillary fossa, 3.6% in SC, and only 0.4% in IM. Age, tumor size, positive axillary lymph nodes(AXLN) number and molecular subtype were independent risk factors for LRR. Tumor size, vessel invasion and positive AXLN percentage were risk factors for CW recurrence. The 5-year CW recurrence rate was 0.9% in patients with 0-1 risk factors compared to 4.6% in those with 2-3 risk factors(p=0.000). For axillary recurrence, tumor size, the positive AXLN number and HER-2 status were prognostic factors. The 5-year axillary recurrence rate differs in risk groups (low: 1.8% vs. high: 7.8%, p = 0.000). ER/PR status, age and positive AXLN number were prognostic factors for SC recurrence. The 5-year SC recurrence rate were also different (low: 3.2% vs. high: 9.4%, p = 0.000). The LRR rate was quite low in N2-3 breast cancer after PMRT. The risk groups for specific sites at risk may help clinicians to recognize the high risk patients and modify the locoregional treatment individually.