The Clinical survival benefit of postmastectomy radiotherapy patients screened from T1-2N1M0 breast cancer according to tumor size and the number of lymph nodes

Abstract

Abstract Purpose our study was aimed at systematically evaluated the advantage of the treatment of postmastectomy radiotherapy (PMRT) on the overall survival (OS) depending on the lymph nodes number and the size of tumors in patients who had breast cancer in stage of T1-2N1. Results There were 29,366 patients included in the last analysis, involving 20,167 (68.7%) cases in the group without PMRT and 9199 (31.3%) cases in the group with PMRT. Multivariable Cox model analysis presented that the treatment of radiotherapy could improve the OS (Hazard ratio HR, 0.89;95%CI 0.83–0.96, P = 0.001)in patients who had breast cancer in stage of T1-2N1M0. The analysis of subgroups according to different categories of tumor burden showed that PMRT did not provide an overall survival advantage in tumor size and lymph node subgroups. The advantages of PMRT are related with an increase in overall survival rate in patients who had tumors 4–5 cm in size and 2 or 3 positive lymph nodes (HR 0.69; 95%CI 0.51–0.94; P = 0.017or HR 0.65; 95%CI 0.44–0.95; P = 0.027, respectively). Patients who had tumors size 2–3 cm and 3 positive lymph nodes benefited from PMRT as well (HR 0.61; 95%CI 0.48–0.78; P < 0.001), but other subgroups of patients did not benefit from PMRT . Conclusion The size of breast cancer tumors and positive nodes number appear to be receivable forecast of overall survival benefits after the treatment of radiotherapy, which may allow clinicians to carry out more accurate and effective PMRT decisions in the clinic, especially for the subgroup who had the low-risk breast cancer. Methods Using data from the SEER program from 2004 to 2015, we calculated the use of PMRT and survival in patients with breast cancer who were in stage of T1-T2 and had 1–3 positive lymph nodes that were diagnosed with invasive breast cancer and underwent mastectomy. Patients were selected according to whether they received postoperative radiotherapy. And 29366 matched patients enrolled in the final analysis were respectively included in the post-mastectomy radiotherapy group (PMRT) and non-radiotherapy group (no-PMRT). We analyzed patients in subgroup analysis who had different positive nodes number and the size of tumors. Overall survival (OS) was calculated with the Kaplan-Meier method in comparison with the survival between different subgroups. We carried out Multivariate Cox proportional hazard models to evaluate the analysis of factors on prognosis and estimated the hazard ratios (HR) and their 95% confidence intervals (CI).