Peptide receptor radionuclide therapy of Merkel cell carcinoma using ¹⁷⁷lutetium-labeled somatostatin analogs in combination with radiosensitizing chemotherapy: A potential novel treatment based on molecular pathology

Few studies have been published on the safety and feasibility of synchronous use of peptide receptor radionuclide therapy (PRRNT), as source of internal radiation therapy, in combination with chemotherapy. In this study we reported a 53-year-old man with stage IV Merkel cell carcinoma (MCC), who underwent synchronous internal radiation therapy and chemotherapy. Based on presumable poor prognosis with chemotherapy only, functional similarities of MCC with other neuroendocrine tumors and available evidence of effectiveness and safety of synchronous use of external beam radiation therapy and chemotherapy in treatment of high-risk MCC patients, our interdisciplinary neuroendocrine tumor board recommended him to add PRRNT to his ongoing chemotherapy. He received 2 courses of ¹⁷⁷Lu-DOTATATE(1, 4, 7, 10-Tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid-1-DPhe1-Tyr3-Thr8-octreotide) in combination with ongoing 8 cycles of liposomal doxorubicin based on standard protocols. Response to therapy was evaluated by ¹⁸F-FDG and ⁶⁸gallium-somatostatin- receptor PET/CT. There was an impressive improvement of the clinical symptoms. However, follow-up PET/CT studies showed mixed pattern of response. Synchronous use of PRRNT and radiosensitizing chemotherapy seems safe and feasible in high risk MCC patients, however, further prospective studies and clinical trials are warranted to provide reliable evidence of possible pitfalls and effectiveness of PRRNT and ⁶⁸Ga-somatostatin-receptor PET/CT in the management of MCC.