Clinical outcomes of adjuvant radiotherapy for nodal negative T1 and T2 breast cancer

Background: The objective of this study was to determine the long-term results of postoperative radiotherapy (RT) in patients with node-negative T1-T2 breast cancer and the prognostic factors affecting these results. Materials and Methods: We retrospectively evaluated 382 node-negative breast cancer patients (pT1a-c, T2) treated with surgery. All patients underwent postoperative RT and 80% of patients received hormone therapy. Prognostic variables included patient characteristics, disease characteristics, and intervention factors. The primary endpoint was overall survival (OS). Survival curves were estimated using the Kaplan-Meier method. Differences in observed survival distributions among patient subgroups were evaluated using a two-sided long-rank test. We applied univariate and multivariate Cox models to evaluate predictive factors. Statistical significance was evaluated at a level of P < 0.05. Results: The median follow-up was 143 months. The 10-, 15-, and 20year OS rates were 92%, 86%, and 80%, respectively. Univariate analysis showed that age (< 45, 45-65, > 65 years; P < 0.0001), comorbidity (P = 0.008), menopausal status (P = 0.03), and tumor stage (T1a-c, T2; P = 0.006) (table 1) were significant predictors of OS. Multivariate analysis showed that age (< 45, 45-65, > 65; P = 0.01) and tumor stage (T1a-c, T2; P < 0.0001) were independent predictors of OS. At age 15 years, the OS rate of patients with T1b, T1c, or T2 stage cancer was 87.5%, 81%, or 77%, respectively. Conclusions: Age and tumor stage were independent prognostic factors for women with node-negative early breast cancer.