Survival and prognostic factors in oligometastatic breast cancer.

Abstract

1089 Background: Clinical guidelines for the treatment of oligometastatic breast cancer (OMBC) propagate multimodality treatment including polychemotherapy and ablative local therapy for all detected disease. The aim of this aggressive approach is prolonged disease remission, or even cure, but randomized data to support this strategy lack and long-term outcomes are not well known. We report prognostic factors, and event-free survival (EFS) and overall survival (OS) in a real world, single center cohort of patients with OMBC with long-term follow-up. Methods: Patients with breast cancer and 1-3 distant metastatic lesions who underwent treatment in the Netherlands Cancer Institute were identified via text mining of medical files. We collected patient, tumor and treatment characteristics as well as recurrence and survival data from the medical records. The Kaplan-Meier method was used to calculate EFS and OS estimates, and Cox regression analyses to assess potential prognostic factors. Results: The cohort included 239 patients (of whom two males), diagnosed between 1997 and 2020. Median follow-up was 75.0 months. Fifty-one percent had hormone receptor (HR)-positive/ human epidermal growth factor receptor 2 (HER2)-negative disease, 20.1% had HER2-positive disease, and 19.2% had triple negative (TN) disease. Median age at OMBC diagnosis was 49.0 years and 47.3% of patients had synchronous disease (metastases ≤6 months of primary diagnosis). Most patients (81.2%) received chemotherapy and local therapy (surgery, radiotherapy and/or radiofrequency ablation) of all metastatic lesions (83.7%). Of 239 patients, 134 experienced disease recurrence with a median EFS of 40.0 months (95% confidence interval (CI): 28.6-51.4); 97/239 died and median OS was 93.0 months (95% CI 74.5-111.5). The table shows factors associated with favorable OS in multivariable analysis. Cox regression analysis for EFS showed similar results. Conclusions: In this large real world cohort of OMBC patients, EFS and OS compare favorably to survival in the general MBC population. HR-positive and/or HER2-positive subtypes, synchronous disease or long DFI, favorable response to first-line systemic therapy and local therapy of all distant lesions are independently associated with better survival. Future studies should be directed at optimizing patient selection and therapy choices in this population with the potential for cure. [Table: see text]