Clinicopathological features and response to platinum-based chemotherapy in pancreatic neuroendocrine carcinoma: A retrospective multicenter study of 70 patients.

Abstract

298 Background: The WHO classified pancreatic neuroendocrine Neoplasms (pNEN) in 2010 as G1, G2, and neuroendocrine carcinoma (NEC). However, pNEC is suspected to include heterogeneous disease entities, but is still not fully studied. We aimed to clarify the clinicopathological and molecular characteristics of NECs. Methods: A total of 100 cases clinical data and pathological slides originally diagnosed as NEC by the WHO in 2010(WHO-NEC) were retrospectively collected from 31 institutes. Expert pathologists were reassessed all cases slide using the designed protocol and reclassified as well differentiated NET (NET-G3), small cell NEC(SCNEC), and large cell NEC(LCNEC) by morphological features. Results: Thirty cases were eliminated mostly because acinar cell carcinoma, NET-G2 and malignant tumor not otherwise specified. Remaining 70 cases were subclassified into 21(30%) NET-G3, 31 (44.3%) SCNEC, 18(25.7%) LCNEC. Comparisons of NET-G3 vs. SCNEC vs. LCNEC revealed the following traits: ENETS stageⅣ: 76%, 81% and 78%; median Ki67 LI: 28.5% (15-53), 85 % (50-100) and 70.0 %(22-90); abnormal Rb expression: 0 %, 59% and 47%; KRAS mutations: 0 %, 48% and 50%; response rates to platinum-based chemotherapy: 0%, 60% and 44.4% ;and median survival(days): 1255, 340 and 196, respectively. When KRAS divided wild (n = 20) and KRAS mutation group (n = 42), response rate to platinum-based chemotherapy was 77% vs 23%.In the same manner, when Rb immune stain divided negative (n = 24) and positive (N = 41), response rate to platinum-based chemotherapy was 80% vs 23.8%. Besides response rate to platinum-based chemotherapy of KRAS mutation(+) and Rb immunopositivity(-) group (n = 7) were 100%, on the other hand, KRAS mutation(-) and Rb immunopositivity(+) group (n = 7) were 18.7%. Conclusions: In this retrospective study, WHO-NEC include 30% NET-G3. NET-G3 are genetically different from SCNEC and LCNEC. As for chemotherapy,Mutated KRAS and/or Rb immunonegativity in tumors with pNEC is associated with response to platinum-based chemotherapy.