Pathologic Complete Response and Oncologic Outcomes in Locally Advanced Breast Cancers Treated With Neoadjuvant Radiation Therapy: An Australian Perspective.

PURPOSE: To assess the degree of pathologic complete response (pCR), postoperative surgical complication rates, and oncological outcomes in women with locally advanced breast cancer or high-risk breast cancers treated with neoadjuvant radiation therapy (NART).

METHODS AND MATERIALS: This retrospective, multi-institutional review involved 138 clinically staged patients with 140 breast cancers treated with NART between January 2014 and February 2021. Treatments involved sequential neoadjuvant chemotherapy and NART, followed by mastectomy with or without axillary surgery and immediate autologous breast reconstruction. Descriptive statistics were used to assess patient and disease features, treatment regimens, pathologic response, and factors affecting postoperative complications. Kaplan-Meier curves were performed to assess locoregional recurrence-free, distant metastasis-free, and overall survival outcomes.

RESULTS: Median age was 47 years (interquartile range, 42-52). The median follow-up was 35.2 months (interquartile range, 17.1-46.5). pCR was achieved in 36.4% (as defined by Chevallier classification) or 42.1% (as defined by Miller-Payne scores) of patients. Greater pCR rates were achieved for HER2+ (73.8%-85.7%) and triple-negative phenotypes (47.6%-57.1%). There were 21 grade 3 surgical complications including 10 grade 3B breast events and 8 grade 3B donor-site events, where surgical reintervention was required. At 3-years' follow-up, the locoregional recurrence-free survival was 98.1%, distant metastasis-free survival was 83.6%, and overall survival was 95.3%%.

CONCLUSIONS: NART is feasible to facilitate a single-stage mastectomy and immediate autologous breast reconstruction. This study demonstrated comparable rates of postoperative complication to standard of care, and high rates of pCR, which translates to high rates of locoregional control, distant metastasis-free survival, and overall survival.