Favorable Response to Treatment with Avelumab in an HIV-Positive Patient with Advanced Merkel Cell Carcinoma Previously Refractory to Chemotherapy

Avelumab is indicated for the management of Merkel cell carcinoma, a rare and aggressive neuroendocrine skin cancer. Its regulatory approval followed the positive outcome of a Phase 2 trial on 88 patients with stage IV disease, which excluded patients with immunodeficiency due to HIV, a risk factor for this cancer type. We report a positive and sustained response to avelumab in an HIV-positive patient with stage IV Merkel cell carcinoma refractory to previous chemotherapy (cisplatin/etoposide) and radiotherapy. Five cycles of avelumab 10 mg/m(2) resulted in the resolution of tumor activity visualized using PET-CT scanning in all affected lymph nodes. The only major side effect associated with avelumab was thyroiditis and mild hypothyroidism, a known adverse effect of this treatment, which was well controlled by L-thyroxine treatment. Treatment is ongoing and the positive response has been sustained during 5 further cycles of treatment up to date. This apparently durable response is consistent with the earlier clinical trial experience with avelumab, but seen here in a patient with HIV-associated immunodeficiency as a predisposing factor (an exclusion criterion from the previous trial). Further clinical trials with avelumab in a broader patient population with Merkel cell carcinoma are warranted.