Can Radiotherapy After Breast-Conserving Surgery be Omitted in Elderly Patients with Early-Stage, Hormone-Receptor Negative Breast Cancer? A Population-Based Study and Proposed Nomogram.

INTRODUCTION

We aimed to evaluate whether radiotherapy (RT) after breast-conserving surgery (BCS) can be omitted in elderly patients with early-stage, hormone receptor-negative breast cancer.

METHODS

Patients aged 65 years and older with T1-2N0-1, hormone receptor-negative breast cancer in 2010-2015 were extracted from the Surveillance, Epidemiology, and End Results program. Propensity score matching was used to balance the baseline of different groups. Survival analysis was performed using Kaplan-Meier plot and log-rank test. Independent risk factors were identified by multivariate Cox analysis. A nomogram predicting breast cancer-specific survival (BCSS) and a risk stratification model were constructed and validated.

RESULTS

A total of 4465 patients were included and 27.7% (1237/4465) patients did not receive postoperative RT. RT was significantly associated with improved overall survival (OS) (HR = 0.552 P < 0.001) and BCSS (HR = 0.559, P < 0.001) in the matched cohort. The same results were found after adjusting independent risk factors by multivariate analysis. On the basis of the nomogram predicting BCSS of patients without RT by incorporating independent risk factors (age, race, HER2 status, T stage, and N stage), we built a risk stratification model which indicated that RT improved OS (HR = 0.511, P < 0.001) and BCSS (HR = 0.517, P < 0.001) in the high-risk group (total score > 150), but not in the low-risk group (total score ≤ 120). The C-index and all calibration curves demonstrated sufficient accuracies and good predictive capabilities.

CONCLUSIONS

RT is indeed beneficial for the whole cohort in this study. However, it may be omitted in the low-risk subgroup without significantly sacrificing survival. For patients in the high-risk group, RT following BCS remained beneficial. This study highlights the need for prospective randomized trials to study RT de-escalation strategies.