Electrochemotherapy of skin metastases from breast cancer: a systematic review

Skin metastases occur in 5-30% of breast cancer (BC) patients. Standard treatments include systemic therapies (chemotherapy, endocrine therapy, and immunotherapy) and local treatments (surgery and radiotherapy). Electrochemotherapy (ECT) could be another option in this setting based on preclinical and clinical studies. Aim of this review was to analyze the available evidence on ECT in skin metastases from BC. Studies reporting on ECT in skin metastases from BC were included in this review. Studies not reporting toxicity or tumor response or not reporting results separately from other primary cancers were excluded. The search was based on Medline, Scopus, and The Cochrane Library databases. Eleven studies including 464 patients were analyzed. ECT was performed using intravenous/intratumoral bleomycin (10 studies) or intratumoral cisplatin (one study). Complete and overall pooled response rates were 46.2% (_95%CI 33.2-59.4 and 74.6% (_95%CI 60.6-86.4) in studies reporting results on a per patient basis and 61.9% (_95%CI 53.8-69.6) and 86.9% (_95%CI 80.0-92.6) in studies reporting results on a per lesion basis, respectively. Worse response rates in larger lesions were observed in three studies. The incidence of toxicity was heterogeneous but adverse events were mild and manageable in all studies. One- and 3-year local progression-free survival was 86.2% and 81.0% in two studies, respectively. ECT is tolerable and effective in terms of response in BC skin metastases especially in less advanced lesions. Further studies are justified to compare ECT with other treatments in this setting.