Prospective multicentre study of patients with cutaneous metastases from breast cancer treated with electrochemotherapy.

Electrochemotherapy (ECT) is a local treatment combining chemotherapy with electroporation. This prospective multicentre study aimed to evaluate the efficacy of ECT in the treatment of patients with skin metastases from breast cancer and confirm whether "luminal A-like" tumors are more responsive to treatment. One-hundred and ninety-five patients were included in the analysis. 55% achieved complete response, 27% partial response (objective response OR 82%); 12% stable disease and 5% experienced progressive disease. The analysis by tumor phenotype showed a significant better response rate in Luminal A-like (p = 0.0060) and Luminal B-like (p = 0.0271) groups compared to Triple-Negative. Patients were divided into 4 groups based on the number and size of cutaneous metastases. Higher response rate was observed in patients with small (≤ 3 cm), single or multiple, metastases (OR rate 95% and 90%, respectively); larger tumors (> 3 cm) showed an OR rate of 85%. Tumor response was not affected by the presence of distant metastases, whereas patients with large cutaneous lesions and distant metastases showed a OR rate of 58%. One-year local progression-free survival (LPFS) was 86% (C.I. 82-89%). In the multivariate analysis, patient age and response to ECT were significantly associated with longer LPFS. This study confirms the efficacy of ECT in small-volume cutaneous metastases from breast cancer regardless the presence of systemic disease and suggests higher efficacy in patients with luminal A- and luminal B-like tumors. ECT can be utilized not only as a palliative measure but also as an alternative treatment for patients not eligible for standard treatments, or in combination with them. Trial registered on https://clinicaltrials.gov/study/NCT06683404 (date of registration 11/11/2024) retrospectively registered.