Background: The management of breast cancer (BC) skin metastases represents a therapeutic challenge. Electrochemotherapy (ECT) combines the administration of bleomycin with temporary permeabilization induced by locally administered electric pulses. Preliminary experience with ECT in BC patients is encouraging.
Methods: A total of 125 patients with BC skin metastases who underwent ECT between 2010 and 2013 were enrolled onto a multicenter retrospective cohort study. The treatment was administered following the European Standard Operative Procedures of Electrochemotherapy. Tumor response was clinically assessed adapting the Response Evaluation Criteria in Solid Tumors, and toxicity was evaluated according to Common Terminology Criteria for Adverse Events 4.0. Cox regression analysis was used to identify predictive factors.
Results: Response was evaluable in 113 patients for 214 tumors (median 1 per patient, range 1-3). The overall response rate after 2 months was 90.2 %, while the complete response (CR) rate was 58.4 %. In multivariate analysis, small tumor size (P < 0.001), absence of visceral metastases (P = 0.001), estrogen receptor positivity (P = 0.016), and low Ki-67 index (P = 0.024) were significantly associated with CR. In the first 48 h, 10.4 % of patients reported severe skin pain. Dermatologic toxicity included grade 3 skin ulceration (8.0 %) and grade 2 skin hyperpigmentation (8.8 %). Tumor 1-year local progression-free survival was 86.2 % (95 % confidence interval 79.3-93.8) and 96.4 % (95 % confidence interval 91.6-100) in the subgroup of those with CR.
Conclusions: In this study, small tumor size, absence of visceral metastases, estrogen receptor positivity, and low Ki-67 index were predictors of CR after ECT. Patients who experienced CR had durable local control. ECT represents a valuable skin-directed therapy for selected patients with BC.