Omission of adjuvant radiotherapy in low-risk elderly males with breast cancer.

PURPOSE: Randomized clinical trials demonstrate that lumpectomy + hormone therapy (HT) without radiation therapy (RT) yields equivalent survival and acceptable local-regional outcomes in elderly women with early-stage, node-negative, hormone-receptor positive (HR +) breast cancer. Whether these data apply to men with the same inclusion criteria remains unknown.

METHODS: The National Cancer Database was queried for male patients ≥ 65 years with pathologic T1-2N0 (≤ 3 cm) HR + breast cancer treated with breast-conserving surgery with negative margins from 2004 to 2019. Adjuvant treatment was classified as HT alone, RT alone, or HT + RT. Male patients were matched with female patients for OS comparison. Survival analysis was performed using Cox regression and Kaplan - Meier method. Inverse probability of treatment weighting (IPTW) was applied to adjust for confounding.

RESULTS: A total of 523 patients met the inclusion criteria, with 24.4% receiving HT, 16.3% receiving RT, and 59.2% receiving HT + RT. The median follow-up was 6.9 years (IQR: 5.0-9.4 years). IPTW-adjusted 5-yr OS rates in the HT, RT, and HT + RT cohorts were 84.0% (95% CI 77.1-91.5%), 81.1% (95% CI 71.1-92.5%), and 93.0% (95% CI 90.0-96.2%), respectively. On IPTW-adjusted MVA, relative to HT, receipt of HT + RT was associated with improvements in OS (HR: 0.641; p = 0.042). RT alone was not associated with improved OS (HR: 1.264; p = 0.420).

CONCLUSION: Among men ≥ 65 years old with T1-2N0 HR + breast cancer, RT alone did not confer an OS benefit over HT alone. Combination of RT + HT demonstrated significant improvements in OS. De-escalation of treatment through omission of either RT or HT at this point should be done with caution.