A Novel Inclusion Criteria for Radiotherapy Omission in Elderly Breast Cancer Patients with Breast-Conserving Surgery.

Background: Breast-conserving surgery (BCS) followed by radiotherapy is the standard treatment for achieving local control and survival benefits in breast cancer patients. However, the necessity of radiotherapy for all elderly patients following BCS is debated due to the potential for overtreatment and the associated risks and side effects, particularly for those at lower risk of recurrence.

Aims: This study aims to redefine the criteria for elderly breast cancer patients eligible for radiotherapy omission after BCS, without compromising survival benefits.

Methods: Data from breast cancer patients with T1-2N0-1M0 diagnosed between 2010 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) program for analysis. Survival analysis was performed using Kaplan-Meier plots and log-rank tests. Univariate and multivariate Cox analyzes were conducted to identify risk factors for breast cancer-specific survival (BCSS). A nomogram and risk stratification model were developed, with a concordance index and calibration curve employed to demonstrate the nomogram's accuracy and predictive capability. Validation of radiotherapy's survival benefit for patients in different risk strata was conducted via subgroup analysis.

Results: Histological grade, estrogen receptor status, tumor size, and nodal metastasis stage were identified as independent risk factors for BCSS. These factors were incorporated into a nomogram to predict 3- and 5-year BCSS for patients. Risk stratification indicated that radiotherapy significantly improved BCSS in the high-risk group (HR = 0.540 [0.402-0.724], P < 0.001) but did not in the low-risk (HR = 0.526 [0.154-1.798], P = 0.305) and intermediate-risk groups (HR = 0.588 [0.33-1.05], P = 0.073). Subgroup analysis showed that some patients not meeting the CALGB 9,343 criteria could also be exempt from radiotherapy. Importantly, we found that patients over 80 years of age did not derive a survival benefit from radiotherapy, regardless of clinical characteristics.

Conclusions: This study broadens the criteria for radiotherapy omission, potentially assisting clinicians in making radiotherapy decisions for elderly breast cancer patients.