The activity and safety of electrochemotherapy in persistent chest wall recurrence from breast cancer after mastectomy: A phase-II study

Electrochemotherapy (ECT) represents an attractive locoregional therapy for unresectable chest wall recurrence (≥WR) from breast cancer. Thirty-five patients with cutaneous CWR after mastectomy who experienced progression despite re-irradiation and extensive systemic treatments were administered bleomycin-based ECT. Local response, toxicity, and superficial control were evaluated. Out of 516 metastases (median 15/patient, range 1-50), response was assessed on 196 target lesions (median size 20 mm, range 10-220). Patients received a median of 2 ECT courses (range 1-3). Two-month objective response was as follows: 54.3 % complete (19/35 patients), 37.1 % partial (13/35), and 8.6 % no change (3/35). Twenty-three patients (65.7 %) developed new lesions (NL) after a median time of 6.6 months (range 2.3-29.5), therefore 1, 2, or 3 ECT cycles were required in 14, 15, and 6 patients, respectively. Median follow-up was 32 months (range 6-53) and the 3-year local control rate was 81 %. Related morbidity was mild, increased after retreatments and consisted primarily of pain (reported as "moderate"/"severe" by 6, 13, and 17 % of patients 1 month after the first, second, and third application, respectively) and dermatological toxicity (acute G3 skin ulceration in 14, 20, and 33 % ofpatients, respectively). Less than 10 metastases (P <0.001), the narrower area of tumor spread on the chest wall (P = 0.022), complete response achievement (P = 0.019), and post-ECT endocrine instead of chemotherapy (P = 0.025) were associated to NL-free survival. Only fewer skin metastases, hazard ratio (HR) 0.122, 95 % confidence interval (≥I) 0.037-0.397, P <0.001, and contained superficial spread, HR 0.234, 95 % CI 0.067-0.818, P = 0.023, were predictors for longer NL-free survival. ECT showed a satisfactory activity in refractory breast cancer CWR, providing sustained local control. Patients with fewer and less scattered skin metastases are less likely todevelop NL. Partial respondersand NL can be handled with additional ECT albeit increasing local pain and skin toxicity.