Abstract / Summary
Abstract Purpose Age-related patterns of radiotherapy utilization and associations between radiotherapy (RT) receipt and overall survival (OS) across surgical settings remain understudied. We evaluated age-specific associations between postoperative radiotherapy receipt and OS and characterized age-related radiotherapy utilization and documented reasons for omission among women with stage I–III breast cancer undergoing breast-conserving surgery (BCS) or mastectomy (Mx) with indications for postmastectomy radiotherapy (PMRT). Methods We conducted a retrospective National Cancer Database cohort study (2004–2021), with follow-up through 2022. Overlap–weighted Kaplan–Meier and Cox models evaluated surgery-radiotherapy comparisons across age strata. Time-varying models assessed immortal-time bias. Marginally standardized logistic regressions estimated adjusted radiotherapy probabilities by age group. Results Among 1,457,243 patients, weighted 5-year OS was 93.2% (95% CI, 93.1–93.3) with BCS + RT and 89.3% (95% CI, 89.2–89.4) with Mx − RT. Corresponding estimates were 89.5% (95% CI, 89.3–89.6) versus 82.6% (95% CI, 82.4–82.9) for radiotherapy versus no radiotherapy after BCS and 82.9% (95% CI, 82.6–83.1) versus 80.5% (95% CI, 80.3–80.8) among PMRT-indicated patients. Age-stratified hazard ratios for radiotherapy ranged from 0.49 to 0.71 after BCS and from 0.77 to 0.94 among PMRT-indicated patients. At age ≥ 75 years, observed RT receipt was 58.6% after BCS and 41.6% among PMRT-indicated patients; adjusted probabilities were 72.1% and 57.1%, respectively. Treatment nonselection and patient refusal predominated among reasons for omission. Conclusion Radiotherapy receipt was associated with higher overall survival across age groups, whereas radiotherapy utilization declined independently with age, supporting individualized radiotherapy decisions beyond chronological age alone.