Impact of adjuvant radiotherapy on survival outcomes in super-elderly patients with triple negative breast cancer: a population-based cohort study

Abstract Background and purpose Super elderly patients (aged ≥ 85 years) with triple-negative breast cancer (TNBC) are markedly underrepresented in clinical trials. The survival benefit of adjuvant radiotherapy (RT) in this population remains unclear. This study aimed to evaluate the impact of adjuvant RT on overall survival (OS) in super-elderly patients with TNBC. We used population-based real-world data for this analysis. Materials and methods We identified patients aged ≥ 85 years with TNBC from 2018 to 2021 in the Surveillance, Epidemiology, and End Results (SEER) database. Patients were grouped by surgery alone or surgery plus adjuvant RT. We used 1:1 propensity score matching (PSM) to balance baseline clinicopathologic and treatment variables. OS was assessed using Kaplan–Meier analysis and the log-rank test. We applied univariate and multivariate Cox models to find independent OS predictors. Analyses included all patients aged ≥ 85 years and a subgroup of those aged ≥ 90 years. Results A total of 838 patients aged ≥ 85 years were included, of whom 272 were nonagenarians. After PSM, 313 patients per group were analyzed in the ≥ 85-year cohort, and 77 patients per group in the ≥ 90-year cohort. Adjuvant RT was associated with improved OS in both age groups; however, these differences did not reach statistical significance (≥ 85 years: HR = 0.71, 95% CI: 0.50–1.02, p = 0.0645; ≥90 years HR = 0.52, 95% CI: 0.27–1.02, p = 0.057). In multivariate analyses, receipt of adjuvant RT was independently associated with improved OS in both cohorts; however, this association may reflect residual confounding from unmeasured variables, and should not be interpreted as evidence of a causal treatment effect. Other factors independently associated with prognosis included T stage, N stage, tumor size, and metastasis status. Conclusions In super-elderly patients with TNBC, adjuvant RT did not lead to a statistically significant OS benefit in propensity score-matched analyses. This lack of significance contrasts with findings in multivariable models, where adjuvant RT was associated with improved OS. As these results are based on an observational design, the observed associations between adjuvant RT and OS improvement should be interpreted with caution.