Calcium Electroporation for Management of Cutaneous Metastases in HER2-Positive Breast Cancer: A Case Report

We report a case of successful treatment of cutaneous metastases in HER2-positive breast cancer with calcium electroporation (CaEP), in addition to trastuzumab, over a period of 5 years. CaEP is performed in local or general anesthesia, by injecting calcium chloride intratumorally and then electroporating cells in the area. Using a handheld needle electrode, a series of short, high-voltage electric pulses are delivered, which transiently permeabilizes cell membranes, causing toxic intracellular calcium levels. The treatment causes cancer cell death, while normal cells are less affected, making the treatment useful for local management of cutaneous lesions. This case presents a 66-year-old female, who had mastectomy surgery followed by adjuvant chemo- and radiotherapy for an ER-negative, HER2-positive breast cancer on her right side in 2003, and a mastectomy followed by endocrine therapy for an ER-positive, HER2 normal breast cancer on her left side in 2006. In 2015, the patient presented local cutaneous recurrence of the ER-negative, HER2-positive breast cancer. The patient was treated with trastuzumab alone, trastuzumab emtansine (TDM1), and a combination of trastuzumab and CaEP. TDM1 was found to have a slightly better effect on the cutaneous metastases than trastuzumab, but the side effects of TDM1 were not acceptable to the patient. The combination of continuous HER2-inhibition and intermittent CaEP, when needed, has been effective in keeping the cutaneous metastases under control for 5 years, and presumably more tolerable for the patient than chemotherapy. An interesting finding was local sparing of calcium electroporated skin from new recurrences, otherwise seen in the general area, which could be a sign of local immunity. This warrants further studies investigating local immunomodulation following CaEP. The patient reported appreciation of a treatment option without chemotherapy, and satisfaction with the outcome of the combination of HER2 inhibition and CaEP treatment. CaEP treatment is currently phase II treatment, and mechanisms and possible applications still need investigation. This novel anticancer treatment could potentially benefit many patients, due to its efficacy, low cost, and accessibility. This case provides observations, which may inspire future trials with CaEP for skin metastases of HER2-positive breast cancer.