Metastasis-directed thermal ablation in patients with metastatic breast cancer and visceral oligoprogression or oligopersistence: a cohort study

Background: Patients with visceral oligoprogressive and oligopersistent metastatic breast cancer (mBC) may benefit from metastasis-directed thermal ablation (TA) to all sites of metastasis, while maintaining the same systemic treatment, in order to delay the time to treatment failure (TTF). This study aims to assess the outcomes provided by this multimodal strategy. Methods: We conducted a single-center, cohort study including consecutive patients with visceral oligoprogressive and oligopersistent mBC as per ESTRO/EORTC criteria, who underwent TA to all sites. Oligoprogression was defined as progressive disease in ≤5 metastatic sites with at least one other metastatic site maintaining the disease control; oligopersistence as ≤5 persistent lesions after systemic therapy. The main endpoint was post-TA progression-free survival (pTA-PFS). Results: 43 patients with oligoprogressive (cohort A) and 43 with oligopersistent (cohort B) disease were included; 4 (5 %) reported a TA-related adverse event. Overall, 122 visceral lesions were treated. In cohort A, median PFS before oligoprogression was 14.9 months (95 % CI, 9.7–20.1). After TA, 32 patients continued the same systemic treatment and 11 switched therapy; pTA-PFS was 9.1 months (95 % CI, 4.8–13.4), unchanged after excluding patients who switched systemic therapy. In cohort B, median PFS before oligopersistence was 7.8 months (95 % CI, 7.4–8.3). After TA, 35 patients continued the same systemic treatment, while 8 de-intensified to maintenance therapy; pTA-PFS was 16.7 months (95 % CI, 11.1–22.2). Conclusion: Selected patients with visceral oligoprogressive and oligopersistent mBC appear to benefit from TA and systemic treatment continuation or modulation. This strategy can be implemented for selected patients in the framework of a multidisciplinary tumor board's shared decision.