A nomogram to predict the benefit of postmastectomy radiotherapy in breast cancer with nodal micrometastases.

BACKGROUND

The role of postmastectomy radiotherapy (PMRT) in breast cancer (BC) with nodal micrometastases (N1mic) remains unclear. This study aimed to evaluate the efficacy of PMRT in T1-2N1mic BC patients who have undergone mastectomy.

METHODS

Female patients with T1-2N1mic BC who underwent mastectomy and were registered in the Surveillance, Epidemiology, and End Results database between 2010 and 2017. The chi-square test, logistic regression analysis, Kaplan-Meier methods, and multivariate Cox proportional hazards analysis were used for statistical analyses. Nomograms for predicting breast cancer-specific survival (BCSS) and overall survival (OS) were created by integrating the independent prognostic factors.

RESULTS

A total of 5948 eligible patients were included in this study. A total of 1207 patients (20.3%) received PMRT, while 4741 patients (79.7%) did not. The use of PMRT increased over the study period, from 15.7% in 2010 to 23.8% in 2017 (P < 0.001). The multivariate Cox proportional hazards analysis showed that PMRT did not improve BCSS and OS. Nomograms were established based on the independent prognostic factors to predict the BCSS and CSS of patients. Regarding BCSS, there were 3627 patients (61.0%) classified as low-risk and 2321 patients (39.0%) classified as high-risk using a cutoff point of 125, PMRT did not improve BCSS in patients with low-risk (P = 0.697) and high-risk (P = 0.149) groups. Regarding OS, there were 4791 patients (80.5%) classified as low-risk and 1157 patients (19.5%) classified as high-risk using a cutoff point of 130, patients who received PMRT had significantly better 5-year OS than those who did not receive PMRT (P = 0.047), while similar outcomes were found between the treatment arms in the low-risk group (P = 0.575).

CONCLUSIONS

While our findings suggest that PMRT does not enhance survival outcomes in T1-T2N1mic BC patients, it may offer a survival advantage in high-risk subgroups.