Abstract PS1-09-10: Effect of Primary Breast Surgery on Prognosis in Breast Cancer Patients with Isolated Bone Metastases

Abstract Background: Breast cancer patients presenting with isolated bone metastases represent a distinct subgroup with relatively favorable prognosis compared to those with visceral metastases. The role of primary breast surgery in this population remains controversial, with limited consensus on its impact on survival outcomes. Clarifying the prognostic effect of surgical intervention on the primary tumor may guide optimal treatment strategies. In this study, we evaluated the impact of primary breast surgery on survival prognosis and other prognostic factors in patients with isolated bone metastases. Method: This retrospective study analyzed data from the Surveillance, Epidemiology, and End Results (SEER) database, including patients with isolated bone metastatic breast cancer, between 2000 and 2021. Relevant demographic and clinicopathological variables were extracted to assess their association with overall survival. Survival analyses were conducted using Kaplan-Meier estimates, and independent prognostic factors were identified through multivariate Cox proportional hazards modeling. Results: A total of 6,500 patients were identified who met the study criteria. 3398 (52.3%) of the patients were under the age of 65. Breast cancer subtype rates were determined as follows: HR+/HER2- (77.2%), HR+/HER2+ (12.8%), HR-/HER2- (6.5%), and HR-/HER2+ (3.5%). All patients had at least one bone metastasis, and there were no other metastases, including distant lymph node metastasis. Surgery was performed in 1513 patients (23.4%). The number of patients who received breast radiotherapy was 124 (1.9%), and the rate of patients who received chemotherapy was 62.8%. The 5-year survival rate was found to be statistically significantly higher in the patient group who underwent surgery (59.5% versus 38.6%) (p<0.001). Other factors were evaluated in terms of prognosis, including age (p < 0.001), gender (p = 0.184), race (p < 0.001), origin (p = 0.331), histopathological subtype (p < 0.001), radiotherapy (p < 0.001), and chemotherapy (p < 0.001). Multivariate analysis confirmed that breast surgery had a statistically significant effect on overall survival (p < 0.001, HR: 0.40). Conclucions: Isolated bone metastatic breast cancer is a special subtype in disease presentation. In recent years, new drugs that improve survival compared to chemotherapy have been introduced in breast cancer, and primary breast surgery should also be considered in selected patients with isolated bone metastatic breast cancer. Citation Format: I. Dogan, A. Azizy, S. Yücel, I. D. Subası, M. Bozkurt, O. Dülgeroğlu, A. Arican, I. Yıldız, C. Uras. Effect of Primary Breast Surgery on Prognosis in Breast Cancer Patients with Isolated Bone Metastases [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-09-10.