The Effect of Radiotherapy on Local Regional Recurrence among Patients with Pathologic Complete Response to Neoadjuvant Chemotherapy in Locally Advanced Breast Cancer

Background: Radiotherapy has been shown to reduce local recurrence rates of breast cancer after treatment with surgery and adjuvant chemotherapy. Indications for postmastectomy radiation have historically been based on pathology, but indications for radiation in the setting of pathologic complete response (pCR) to neoadjuvant chemotherapy are not well defined. The aim of this study was to evaluate the rates of local regional recurrence (LRR) among patients with pCR to neoadjuvant chemotherapy followed by surgery with or without radiation (XRT).Patients and Methods: The case histories of 337 patients with locally advanced breast cancer treated with neoadjuvant chemotherapy, surgery with or without radiation from October 1997 to December 2006 were analyzed. Median age at diagnosis was 50.6 years (range: 25-84). The clinical stage at diagnosis was I in 3 (1%), IIA in 105 (31%), IIB in 94 (28%), and III in 135 (40%) patients. All patients received preoperative systemic therapy with a doxorubicin-based regimen (92%) or a single-agent taxane regimen (7%) or CMF (1%). A total of 272 patients received radiation following surgery and 65 did not receive any radiation. Median follow-up time was 40 months among all patients. The Kaplan-Meier method and log rank test were used to evaluate LRR rates and overall survival among both groups.Results: Patients treated with neoadjuvant chemotherapy followed by surgery and XRT had a lower incidence of LRR at 3 years with 24 cases of local recurrence among 272 patients who received XRT compared with 12 cases of local recurrence among the 65 patients who did not receive XRT (8.9% v 18.5%, P=0.02). Radiation also reduced local regional recurrence at 3 years among a subset of patients with clinical stage T2N1 disease (4.9% v 28.6%, P=0.03). There was no difference in overall survival or disease free survival among patients who received XRT compared to patients who did not receive XRT. There were 62 (18%) patients who achieved a pCR to neoadjuvant chemotherapy. Among patients with a pathologic complete response, radiation appeared to reduce the risk of LRR compared to patients who did not receive XRT (7.4% v 25%, P=0.17).Conclusion: Radiotherapy significantly reduced local regional recurrence rate among patients with locally advanced breast cancer treated with neoadjuvant chemotherapy and surgery. Of particular interest, patients who achieve a pathologic complete response to neoadjuvant chemotherapy still had high LRR rates and may benefit from radiotherapy by lowering the risk of local regional recurrence. Further studies on the significance of LRR and overall survival among these patients are needed. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 4114.