Abstract P1-20-19: Local therapy and its association on survival outcomes in patients with de novo stage IV breast cancer: Results from a retrospective cohort study

Abstract Background: Stage IV breast cancer was considered to be an incurable disease with a poor survival outcome. Among them, patients with de novo stage IV breast cancer (BC) account for approximately 25%. Systemic therapy has remained the cornerstone of treatment, and the role of local therapy (Surgical resection of the primary tumor and/or radiotherapy) for de novo stage IV BC remains controversial. Aim: This study was conducted to examine the clinical and pathological profile and survival outcomes of patients with de novo stage IV BC treated with local therapy at our institutions. Settings and design: The study was conducted at two Chinese tertiary hospitals and was retrospective in nature. Methods and patients: All de novo stage IV BC patients (all female) treated with local therapy and systemic therapy alone at our hospitals between March 2007 and November 2016 were enrolled in the study. Data were retrospectively extracted from the patients’ case records. Data were analyzed according the clinicopathological features and treatment outcomes. Overall survival was used as the primary study outcome. Univariable and multivariable Cox regression analysis were used to assess the association between local therapy and overall survival. Further stratified survival analysis was used to assess the effect of surgical resection of the primary tumor before or after systemic therapy on survival outcomes. Kaplan-Meier method was used for survival analysis and the outcome variables were compared using the log-rank test. Results: A total of 138 cases of de novo stage IV BC patients admitted to our institutions were included, of whom 80 underwent local treatment. There was no significant difference in age, primary tumor N-stage, Ki-67 index, ER/PR status, and HER-2 expression between local treatment group and systemic therapy group. But there were differences in tumor size and metastatic site between the two groups. Surgical resection of the primary tumor was performed in 71/138 (51.4%) patients and 26 cases of the patients had combined radiotherapy. The median duration of follow-up was 31±20.6 months. Median survival time of all patients was 32.1 months, and the 3-year and 5-year survival rates were 36.2% and 12.3%, respectively. The median survival time of local treatment group and systemic therapy group were 38.0 and 19.0 months (HR 0.50; 95% CI 0.34-0.73; p<0.0001), and the 3-year and 5-year survival rates were 53.5% versus 20.9% and 16.9% versus 7.5%, respectively. Similarly, patients who had surgery were found to have a better survival outcome than the patients with non-surgery therapy (HR 0.53; 95% CI 0.36-0.77; p<0.0001). While receipt of radiotherapy alone to either the primary and/or metastatic sites had no impact on overall survival (p=0.24). Interestingly, surgical resection of the primary tumor, whether before or after systemic therapy (p=0.0004; p=0.0005), was independently associated with improved overall survival when compared to systemic therapy alone. Conclusions: Our data support that local therapy mainly based on surgical resection of the primary tumor can improve overall survival in patients with de novo stage IV BC, but fail to demonstrate the survival benefit from radiotherapy alone. However, prospective evidence from phase-3 randomized controlled trials on the feasibility of local therapy in de novo stage IV BC is required before its routine use can be recommended. Key words: De novo stage IV breast cancer; Local therapy; Surgical resection of the primary tumor; Survival outcomes Research protocol number: 2017-AF29-058 Citation Format: Ren Chongxi, Sun Jianna, Kong Lingjun, Liu Hong. Local therapy and its association on survival outcomes in patients with de novo stage IV breast cancer: Results from a retrospective cohort study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-20-19.