Abstract P3-19-26: The impact of post-mastectomy radiotherapy on the survival of breast cancer patients aged 70 years or older: A study based on SEER database

Abstract

Abstract The impact of post-mastectomy radiotherapy on the survival of breast cancer patients aged 70 years or older: a study based on SEER databaseIntroduction: This study aimed to investigate the role of post-mastectomy radiotherapy (PMRT) in the female aged 70 years or older diagnosed with breast cancer, which is still controversial.Methods: This retrospective study extracted data from the Surveillance, Epidemiology, and End Results (SEER) database. Women aged 70 years or more diagnosed with breast cancer between 2004 and 2016 following mastectomy were enrolled. Propensity score matching (PSM) was performed to reduce covariable imbalance. The univariable and multivariable analyses calculated the prognostic factors. Kaplan-Meier survival curves and multivariable Cox regression model were applied to compare breast cancer-specific survival (BCSS) and overall survival (OS) between two arms and among subgroups stratified by various clinicopathological factors. Results: Of the 27,636 female were eligible, 17.2%(n=4,747) received PMRT while 82,8%(n=22,889) not. By multivariable Cox analysis, radiotherapy was still founded to be independent prognostic factors for BCSS and OS. After 1:1 matching, PMRT were associated with significant improvement in BCSS and OS(p <0.001). By contrast, the BCSS and OS benefit from PMRT were not statistically significant in patients with T1 tumor and 1-3 positive lymph nodes(BCSS:HR = 0.716,95%CI 0.406-1.263,p = 0.249;OS:HR = 0.908,95%CI 0.648-1.270,p = 0.572), and the results were consistent in patients with T2 tumor and 1-3 positive lymph nodes(BCSS:HR = 0.866,95%CI 0.664-1.130,p = 0.289;OS:HR = 0.879,95%CI 0.732-1.055,p = 0.166). Stratified by grade, number of positive lymph nodes, and HR status, there were still not survival advantage of PMRT observed for patients with T1-2N1 breast cancer(all p>0.05).Conclusions: This study demonstrates that post-mastectomy radiotherapy has a definite role in improving the survival of females with elderly breast cancer. After a comprehensive assessment of the side effects and the quality of life, the omission of PMRT could be considered in patients with T1-2N1 breast cancer. Citation Format: Jingyi Lin, Shiping Luo, Jie Zhang, Chuangui Song. The impact of post-mastectomy radiotherapy on the survival of breast cancer patients aged 70 years or older: A study based on SEER database [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-19-26.