Postmastectomy radiation therapy and survival outcome in older patients with T1-2N1 breast cancer

Background: The prognostic impact of postmastectomy radiation therapy (PMRT) on contemporary older patients with T1-2N1 breast cancer is unclear. We aimed to investigate the effect of PMRT in this setting. Methods: Leveraging the Surveillance, Epidemiology, and End Results (SEER) program data from 2004 to 2015, 7052 patients aged 70 years or older with T1-2N1 breast cancer were identified for this propensity-matched analysis. Fine and Gray competing risks regression was conducted to explore the correlation between PMRT and breast cancer-specific survival, in subgroups defined by tumor size and positive lymph nodes. Results: The median follow-up was 60.1 months (interquartile range, 28.0 to 87.0). Among propensity-matched patients, multivariate analysis identified an association between PMRT and decreased breast cancer mortality (BCM; HR 0.637; 95 % CI 0.436–0.931; P = 0.020) in patient subset with three positive nodes and tumors 2–5 cm in size, and this benefit was limited to patients with three positive nodes and tumors 2–5 cm in size who did not receive chemotherapy. In patient subsets who received chemotherapy, no association between PMRT and BCM was found. Conclusion: PMRT was not associated with BCM in older patients with T1-2N1 breast cancer who received chemotherapy. The benefit of PMRT was limited to those with three positive nodes and tumors 2–5 cm in size who did not receive chemotherapy