Expanding the Indication for Novel Theranostic 177Lu-Dotatate Peptide Receptor Radionuclide Therapy: Proof-of-Concept of PRRT in Merkel Cell Cancer

The field of theranostics is a new nuclear medicine tool being utilized in the treatment of different types of cancers. It couples receptor-specific based imaging predicting and guiding response to receptor-specific based radionuclide therapies. For example, somatostatin-receptor based imaging (Gallium; 68Ga-dotatate scan) is now predicting and guiding the use of treatment with the somatostatin-receptor radiolabeled somatostatin analog (peptide receptor radionuclide therapy PRRT - Lutetium; 177Lu-Dotatate) for neuroendocrine tumors that express the somatostatin receptors. The United States Food and Drug Administration approved the use of 177Lu-Dotatate PRRT for somatostatin-receptor-positive gastroenteropancreatic neuroendocrine tumors only. Here we show proof of concept and results of an outstanding response to this novel therapy in conjunction with immunotherapy in a refractory cancer type where it has not been approved (Merkel Cell Cancer). Our results and data provide proof of principle for considering the use of this novel therapy in a tumor-agnostic approach; similar to approval of immunotherapy for mismatch repair deficient tumors. The response demonstrated has also been unprecedented, likely secondary to use of PRRT with immunotherapy. These observations have profound and broad implications on how to move this novel field of theranostics forward for treatment of many cancer-types.