Abstract P5-14-02: Postmastectomy radiation improves loco-regional control for patients with advanced breast cancer treated with neoadjuvant chemotherapy
Authors: Fujita T , Sawaki M , Hattori M , Naoto K , Horio A , Gongou N , Ichikawa M , Idota A , Adachi Y , Hisada T , Kotani H , Ishiguro J , Iwata H 
Published: August 2014

Abstract
Purpose
The value of postmastectomy radiation (PMRT) with adjuvant chemotherapy has been established, but the role of PMRT after neoadjuvant chemotherapy remains unclear.
The aim of this study was to evaluate the efficacy of radiation in patients treated with neoadjuvant chemotherapy and mastectomy, and to determine which subsets of patients benefit from PMRT.
Patients and Methods
From 2003 to 2008, 94 patients were treated with neoadjuvant chemotherapy and mastectomy. The median number of lymph nodes removed was 20. 90 patients received anthracycline-based (anthracycline alone: 5, anthracycline followed by taxane: 85) chemotherapy and 4 patients received taxane alone. 82.6 percent (19/23) of the patients with HER2 positive cancer received trastuzumab and 91.3 percent (63/69) of the patients with hormone receptor positive cancer received hormone therapy. In this study, pathological complete response (pCR) was defined as absence of invasive tumor in the breast.
We compared the outcomes of 55 patients who received radiation (PMRT group) from 39 patinets who did not receive radiation (non-PMRT group).
The 5 years rate of loco-regional recurrence (LRR) was calculated according to the Kaplan-Meier method, and comparisons between the two groups were made using the log-rank test.
Results
Median follow-up time was 61.8 months. The breast pCR rate was 17.0% (16/94). 14 patients developed LRR as first events (local: 8, regional: 4, local and regional: 2). There were no differences between the two groups with respect to age, use of trastzumab, use of hormone therapy, pathological tumor size, number of dissected axillary nodes, percentage of hormone receptor positive tumors, or HER2 positive tumors.
The 5-years rate of LRR for the PMRT group and the non-PMRT group were 12.8% and 27.0% respectively. (p = 0.144) In the patients with positive lymph nodes after neoadjuvant chemotherapy, the PMRT group had significantly lower LRR risk than the non-PMRT group (5-yaers rate: 11.9% vs 37.5%, p = 0.039). But in the patients with negative lymph node, there were no significant difference between the PMRT group and the non-PMRT group. For hormone receptor positive and HER2 negative subtype, a significantly improved LRR risk found after PMRT (5-yaers rate: 5.9% vs 26.1%, p = 0.048). No significant difference in HER2 positive subtype and triple negative subtype were observed between two groups. In the patients who did not achieve breast pCR, the PMRT group had significantly lower LRR risk than the non-PMRT group (5-yaers rate: 9.0% vs 30.6%, p = 0.037). The 5-years rate of lymphedema was no significant difference between the two groups (p = 0.787).
Conclusion
After neoadjuvant chemotherapy and mastectomy, PMRT was found to benefit local control for the patients with positive lymph nodes, the patients with hormone receptor positive and HER2 negative cancer, and the patients who did not achieve breast pCR.
Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-14-02.