Predictive factors to ECT response in breast cancer cutaneous and subcutaneous metastases have been previously investigated in small studies and some have been reported (e.g., small tumor size, absence of visceral metastases, estrogen receptor positivity, low Ki-67 index, lower body mass index, reduced body surface, absence of previous radiation treatment, concurrent systemic therapies) [7,8,10,16]. This evidence concerns the gene ESR1 and breast cancer.