Immunotherapy with Imiquimod and Interferon Alfa for Metastasized Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine tumour of the skin. Remission rates are high with chemotherapy in patients with metastasis, but without any improvement in overall survival. We present the case of a 90-year-old woman with facial MCC. After radiation and surgery, the MCC recurred with widespread cutaneous and regional lymph node metastases. The metastases were treated with weekly intralesional injections of 1–2×10⁶ IU interferon alfa-2a, accompanied by topical imiquimod 5% cream 3 times weekly. After partial regression, subcutaneous pegylated interferon alfa-2b was added at a dose of 30 μg weekly, which was then increased to 50 μg weekly. At 4 months after the start of immunotherapy, all cutaneous metastases and the intralesionally treated lymph node metastases receded. Interruption or reduction of systemic interferon application resulted in locoregional relapses that were successfully treated with surgery or intralesional interferon injections. The patient remains alive 30 months after initiation of immunotherapy, suggesting that locally metastasized MCC might be able to be controlled with local and systemic immunotherapy.