Abstract PO4-23-04: Is breast-conserving surgery an optional local therapy for non-inflammatory skin involvement (T4b) breast cancer? A Propensity Score Matching and Inverse Probability Weighting Analysis of SEER Database Results

Abstract Introduction: Although breast-conserving surgery (BCS) usage has been widespread in breast cancer treatment, it is still controversial about its application in non-inflammatory skin involvement (T4b) breast cancer. We designed this study to compare the prognosis for BCS versus mastectomy in this population. Methods: This retrospective cohort study included patients from the SEER database diagnosed with tumor stage T4b breast cancer from 1998 to 2019. To create prognostic factors, balance between BCS+RT and Mastectomy+RT groups, we calculated propensity scores for each patient. The calculation was based on the advance assessment for factors affecting prognosis, with the use of univariable and multivariable Cox proportional hazards models. Based on it, two propensity score-based matchings were conducted, including propensity score matching (PSM) and inverse probability weighting (IPTW). After adjustment, we performed Kaplan-Meier curves and multivariable Cox proportional hazards models to estimate BCSS and OS. Results: Of 4,680 patients who met the criterion, 588 received BCS+RT, and 4092 received Mastectomy+RT. In the propensity score matching (PSM) cohort, BCS+RT was found to improve breast cancer cause-specific survival (HR, 0.67; 95% CI, 0.53 to 0.85; p=0.001) and overall survival (HR, 0.72; 95% CI, 0.59 to 0.88; p=0.001). Similar results in the analysis of the IPTW-matched cohort confirm this result (BCSS: HR, 0.672; OS: HR, 0.722). Subgroup analysis revealed that those less than 70 years old, grade I+II, 3cm or smaller tumor size, hormone receptor-positive, or received chemotherapy treatment were more likely to benefit from BCS+RT (all p 0.05). Conclusions: Locally treatment with BCS usage presented a significantly better survival than with mastectomy for non-inflammatory skin involvement (T4b) breast cancer patients. This finding provided evidence of selection in the local treatment of these patients. Citation Format: Jingyi Lin, Shiping Luo, Jie Zhang, Chuangui Song. Is breast-conserving surgery an optional local therapy for non-inflammatory skin involvement (T4b) breast cancer? A Propensity Score Matching and Inverse Probability Weighting Analysis of SEER Database Results abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-23-04.