Breast surgery and systemic treatment continuation for patients with de novo metastatic breast cancer and locoregional oligoprogression: a cohort study

Background: The role of breast surgery in patients with de novo metastatic breast cancer (mBC) and locoregional oligoprogression, either in the breast or locoregional lymph nodes, who previously had a response to systemic treatment is unknown. This approach may allow maintenance of the same systemic treatment and prolong the time to treatment failure. Patients and methods: We conducted a cohort study including consecutive patients with de novo mBC, after a locoregional oligoprogression, who underwent breast surgery and continued the same systemic treatment at the European Institute of Oncology. The primary endpoint was postsurgery progression-free survival (pS-PFS). Results: Fifty-nine patients were included: 28 (47%) had hormone receptor (HR)-positive/human epidermal growth factor receptor 2 (HER2)-negative disease, 30 (51%) HER2-positive, and 1 (2%) triple-negative. The median pre-oligoprogression PFS was 15.2 months [95% confidence interval (CI) 12.0-18.4 months]. After a median follow-up of 54.1 months (95% CI 44.2-64.0 months), the median pS-PFSs was 15.0 months (95% CI 5.1-24.9 months), and was significantly longer in patients with HER2-positive disease or with a pre-oligoprogression PFS ≥12 months. Conclusions: This study suggests that selected patients with de novo mBC and locoregional oligoprogression can benefit from breast surgery while maintaining the same systemic treatment, particularly in the setting of HER2-positive disease or a pre-oligoprogression PFS >1 year.