The Role of Postmastectomy Radiation Therapy in Patients With Breast Cancer Responding to Neoadjuvant Chemotherapy

When surgery is the first line of breast cancer treatment, numerous randomized clinical trials and meta-analyses have demonstrated that postmastectomy radiation therapy (PMRT) improves locoregional control and survival for many women with axillary lymph node–positive disease. In contrast, there are no randomized data regarding the use of PMRT in women who receive neoadjuvant chemotherapy (NAC) first followed by mastectomy. This has led to controversy regarding which patient with breast cancer will benefit from PMRT after NAC, particularly in women with clinically node-positive axillary disease that responds well and is down staged to pathologically negative disease at surgery (ypN0). We review the current evidence on this topic, which forms the underlying basis for the ongoing phase III clinical trial—National Surgical Adjuvant Breast and Bowel Project (NSABP) B51/RTOG 1304—that is examining the role of regional nodal irradiation in patients with clinical N1 disease that responds to NAC and becomes ypN0 at surgery.