Interval Of Up To 16 Weeks Between Mastectomy And Radiation Does Not Impair Locoregional Outcome In Patients Receiving Neoadjuvant Chemotherapy

There is no data to define an appropriate time interval between surgery and radiation in patients receiving neoadjuvant chemotherapy (NACT), mastectomy, and post-mastectomy radiation (PMRT). We evaluated the impact of delay in initiation of PMRT in breast cancer patients treated with NACT in a cohort of medically underserved patients with multiple barriers to timely care, with a wide range of intervals between surgery and PMRT. We retrospectively reviewed medical records of 258 consecutively treated patients between 1/1999 and 12/2009. We collected data on patient demographics, disease and treatment characteristics, and locoregional recurrence (LRR), progression free survival (PFS) and overall survival (OS). Patient demographics: 25.2% African descent, 74.8% white/other; 70.9% Hispanic, 29.1%, non-Hispanic; 54.3% age ≤ 50. Disease characteristics: 46.9% ER+ Her2-, 38.4% ER- Her2-, 6.6% ER + Her2+, 7.4% ER- Her2+; 35.7% clinical stage II, 52.7% stage III, and 11.2% inflammatory. Treatment characteristics: all patients had NACT followed by mastectomy with axillary lymph node dissection; none had adjuvant chemotherapy (with the exception of trastuzumab or other drugs delivered concurrently with radiation). 24.8% had pathologic complete response in the breast + axilla, and 48.3% in the axilla. All patients received radiation (RT) to CW +/- regional lymph nodes, median total dose inclusive of boost 60.4 Gy (range, 46.8-74.4). The median interval from surgery to PMRT was 11.6 weeks (range, 2 to 109.3). 22.9% of patients started PMRT within 8 weeks of surgery, 53.1% within 12 weeks, and 67.8% within 16 weeks. Median follow-up from date of diagnosis was 35.6 months (range, 7.7 - 104.6). There were 12 LRR. The median interval from surgery to PMRT in those with LRR was 10 weeks (range, 7.1-36). The cumulative 5-year incidence of LRR as first site of failure (+/-synchronous distant failure) was 6.6% (95% CI 3.5-11). There was no statistically significant difference in locoregional outcome among patients starting PRMT within 8 weeks (p = 0.581), 12 weeks (p = 0.366), or 16 weeks (p = 0.498) after surgery on univariate analysis, or multivariate analysis controlling for race, receptor status, or nodal stage. The 5-year progression-free survival was 75.4% (95% CI 67.7-81.5) and overall survival 84.1% (95% CI 75.7-89.7). In a cohort of breast cancer patients uniformly treated with NACT, mastectomy, and PMRT, delays in the initiation of radiation of up to 16 weeks after surgery did not impact locoregional outcome. Although timely initiation of PMRT remains a priority, the locoregional control benefit of PMRT appears to be maintained up to at least 16 weeks from surgery in patients receiving NACT.