Postmastectomy radiotherapy (PMRT) has been strongly considered for patients with 1-3 positive axillary nodes (ALNs). In addition, the indications for PMRT are expanding to patients with negative ALNs but have multiple high-risk recurrence factors. However, For patients with isolated tumor cells. We aimed to determine the effects of PMRT on survival of patients with ITCs or ALNs micrometastases of breast cancer.
We identified patients with ITCs or ALNs micrometastases after mastectomy from the Surveillance, Epidemiology, and End Results database from 2004 to 2014. Overall survival (OS) and breast cancer-specific mortality (BCSM) were compared among patients received PMRT or not, using propensity score-matched analyses. Cox proportional hazards models and competing-risk models were performed in OS and BCSM analyses, respectively.
We identified 11,622 eligible cases. PMRT was administered to 1,728 patients. Treatment was less frequent among patients who were older, patients with high-income, and patients with right-side tumor. OS at 5 years and 10 years were 88.1% and 74.2% in PMRT group, and were 87.8% and 77.3% in non-PMRT group, respectively. Five-year and 10-year cumulative BCSM rate were 6.4% and 12.3% in PMRT group, and were 6.6% and 14.1% in non-PMRT group, respectively. OS and BCSM were unaffected by PMRT after adjusting for multiple confounders (OS, hazard ratio, 0.92; 95% CI, 0.74 to 1.16; BCSM, subhazard ratio, 0.89; 95% CI, 0.67-1.18).
To our knowledge, this is the largest study to date of the effect of radiotherapy on survival in breast cancer with ITCs or ALN micrometastases. In this population-based study, we do not find survival benefit of PMRT on patients with ITCs or ALN micrometastases.
Clinical trial identification
Legal entity responsible for the study
Sun Yat-sen University Cancer Center
All authors have declared no conflicts of interest.