Impact of surgery-radiation interval on locoregional outcome in patients receiving neo-adjuvant therapy and mastectomy.

Delays in the initiation of radiation are increasingly common for medically underserved patients. We evaluated the impact of delay in initiation of postmastectomy radiation (PMRT) in breast cancer patients treated with neo-adjuvant therapy (NAT) in a cohort of medically underserved patients with multiple barriers to timely care. We retrospectively reviewed medical records of 248 consecutively treated patients. Clinical stage was 34.4% II, 65.6% III. The median interval from surgery to PMRT was 11.9 weeks; 22.2% started PMRT within 8 weeks of surgery, 52% within 12 weeks, and 67.3% within 16 weeks. The cumulative 5-year incidence of locoregional recurrence (LRR) was 5.8% (95% CI: 3.2-9.7). There was no significant difference in locoregional outcome among patients starting PMRT within 8 weeks versus >8 weeks (p = 0.634), ≤ 12 versus >12 weeks (p = 0.332), or ≤ 16 versus >16 weeks (p = 0.549) after surgery. Although timely initiation of PMRT remains a priority, the locoregional control benefit of PMRT appears to be maintained up to at least 16 weeks, and in those without early locoregional recurrence, PMRT should be offered despite such a delay.