The prognostic influence of the proliferative discordance in metastatic pancreatic neuroendocrine carcinoma revealed by peptide receptor radionuclide therapy Case report and review of literature

Rationale: Pancreatic neuroendocrine tumors (pNET) are rare slowly growing tumors with a high metastatic potential. Peptide receptor radionuclide therapy (PRRT) with radiolabeled analogues has been developed as a new tool for the management of metastatic well-differentiated (grade 1 and 2) neuroendocrine tumors expressing somatostatin receptor (SSTR2). Chemotherapy is the mainstay in the management of grade 3 (G3) unresectable pancreatic neuroendocrine carcinoma (pNEC). To date, no study has evaluated the efficacy of PRRT in such tumors. Diagnoses and interventions: We describe a case of a progressive G3 pNEC with huge liver metastases successfully treated with PRRT (177Lu DOTATATE). Outcomes: Complete remission was obtained for 3 years. Indeed, the mitotic index was low (as G2 tumors) but with a very high Ki67 index (45%-70%). Such discordance between the proliferative markers should consider the use of PRRT before chemotherapy in unresectable metastatic G3 tumors expressing SSTR2. Lessons: This case supports the hypotheses highlighting the heterogeneity of G3 pNEC. The latter should be subdivided into 2 distinct categories: proliferation-discordant (well differentiated) and concordant (poorly differentiated) NEC. PRRT could be suggested for the former group before the conventional chemotherapy.