Three Cases of Merkel Cell Carcinoma Treated With Lutetium-177 Oxodotreotide.

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine skin cancer associated with early metastasis and poor outcomes in the advanced stages. Immune checkpoint inhibitors (ICIs), particularly avelumab, represent the first-line therapy for metastatic MCC. However, effective treatment options after progression or intolerance remain limited. Peptide receptor radionuclide therapy (PRRT) using radiolabeled somatostatin analogs has emerged as a potential therapeutic option for tumors expressing somatostatin receptors (SSTRs). We present three patients with advanced MCC (aged 73, 45, and 77 years, respectively) treated with 177Lu-oxodotreotide after failure or intolerance of ICI therapy and cytotoxic chemotherapy. 111In pentetreotide single photon emission computed tomography/computed tomography demonstrated SSTR uptake in all patients, supporting the rationale for PRRT. All patients ultimately experienced disease progression; however, one achieved transient disease stabilization with tumor reduction. The times from the first PRRT administration to death were 3.4, 4.2, and 1.4 months, respectively. No serious treatment-related adverse events were observed. These findings suggest that 177Lu-oxodotreotide may represent a feasible and relatively safe option for patients with treatment-refractory MCC, although its antitumor efficacy is limited. However, further prospective studies are required to elucidate its clinical role.