Successful treatment of localized Merkel cell carcinoma with avelumab in a patient with amyotrophic lateral sclerosis.

Currently, the first-line treatment of non-metastatic Merkel cell carcinoma (MCC) is complete resection. In case of unresectable or metastatic MCC, immune checkpoint inhibitor (ICI) therapy with avelumab (or in the US also pembrolizumab or retifanlimab) is indicated. We report on a patient with a primary, non-metastatic MCC on the left eyelid and amyotrophic lateral sclerosis (ALS). Due to ALS, the patient's communication was limited to eye movement and blinking. Complete resection or definitive radiotherapy of the tumor while preserving the function of the eye muscles was not possible. No prior data was available for patients with ALS under ICI therapy. In agreement with the patient and his family, a monotherapy with avelumab, a programmed death ligand 1 (PD-L1) inhibitor, was initiated. This led to a complete remission of the tumor with a progression-free survival of over 24 months and importantly no deterioration of the ALS.