Determinants of delayed postoperative radiation therapy in breast cancer patients undergoing neoadjuvant chemotherapy: A subanalysis of the AMAZONA III prospective cohort

BACKGROUND: Delays in starting postoperative radiation therapy (PORT) in breast cancer patients may be associated with poorer clinical outcomes. This analysis aimed to identify factors contributing to delayed PORT in patients with breast cancer who underwent neoadjuvant chemotherapy followed by surgery and PORT in a Brazilian cohort. METHODS: Participants were categorized based on the interval from surgery to the initiation of PORT into two groups: ≤ 8 weeks and > 8 weeks. Socioeconomic and clinicopathological factors were analyzed for associations with delayed PORT. Univariable and multivariable regressions were performed. RESULTS: Factors significantly associated with delayed PORT included low educational level (RR: 1.50; 95 % CI: 1.05-2.14; p = 0.0276), public health insurance (RR: 3.29; 95 % CI: 1.76-6.12; p = 0.0002) and having a Luminal A or Luminal B-HER2-negative subtype (RR: 1.92; 95 % CI: 1.14-3.23; p = 0.0153) compared to the Triple Negative subtype. The absence of adjuvant endocrine therapy was associated with a lower risk of delayed PORT (RR: 0.67; 95 % CI: 0.46-0.99; p = 0.0338). In the multivariate analysis, public health insurance remained the sole independent predictor of delayed PORT (RR: 2.98; 95 % CI: 1.60-5.55; p = 0.0006). CONCLUSION: In this cohort, reliance on public health insurance emerged as the primary independent predictor of delayed initiation of PORT in breast cancer patients who received neoadjuvant chemotherapy. Lower educational levels and household income also contributed to delays, highlighting disparities within the healthcare system. Addressing these barriers is essential for improving timely access to PORT and potentially enhancing clinical outcomes in this population.