High-grade (HG) gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN) are rare but have a very poor prognosis and represent a severely understudied class of tumours. Molecular data for HG GEP-NEN are limited and treatment strategies for the carcinoma subgroup (HG GEP-NEC) are extrapolated from small-cell lung cancer (SCLC). After pathological re-evaluation, we analysed DNA from tumours and matched blood samples from 181 HG GEP-NEN patients; 152 neuroendocrine carcinomas (NEC) and 29 neuroendocrine tumours (NET G3). Based on sequencing of 360 cancer related genes, we assessed mutations and copy number alterations (CNA). For NEC, frequently mutated genes were TP53 (64%), APC (28%), KRAS (22%) and BRAF (20%). RB1 was only mutated in 14%, but CNAs affecting RB1 were seen in 34%. Other frequent copy number losses were ARID1A (35%), ESR1 (25%) and ATM (31%). Frequent amplifications/gains were found in MYC (51%) and KDM5A (45%). While these molecular features had limited similarities with SCLC, we found potentially targetable alterations in 66% of the NEC samples. Mutations and CNA varied according to primary tumour site with BRAF mutations mainly seen in colon (49%), and FBXW7 mutations mainly seen in rectal cancers (25%). 8/152 (5.3%) NEC were microsatellite instable (MSI). NET G3 had frequent mutations in MEN1 (21%), ATRX (17%), DAXX, SETD2 and TP53 (each 14%). We show molecular differences in HG GEP-NEN, related to morphological differentiation and site of origin. Limited similarities to SCLC and a high fraction of targetable alterations indicates a high potential for better personalized treatments.

High-grade gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are classified according to morphology as well-differentiated neuroendocrine tumours (NETs) G3 or poorly differentiated neuroendocrine carcinomas (NECs). Little data exist concerning which morphological criteria this subdivision should be based on. Uncertainty exists if the NEC group should be further subdivided according to prolifera-tion rate. Clinical data on NET G3 and NEC with a lower Ki-67 range are limited. A total of 213 patients with high-grade GEP-NEN (Ki-67 >20%) were included from the Nordic NEC Registries. Four experienced NET pathologists re-evaluated the cases to develop the best morphological criteria to separate NET G3 from NEC, assuming longer survival in NET G3. Organoid growth pattern, capillary network in direct contact to tumour cells, and absence of desmoplastic stroma were found to best separate NET G3 from NEC. Of 196 patients with metastatic disease, NET G3 was found in 12.3%, NEC with a Ki-67 <55% (NEC < 55) in 29.6%, and NEC with a Ki-67 Hege Elvebakken and Aurel Perren contributed equally to this work. Eva Tiensuu Janson and Halfdan Sorbye shared last authorship.

High-grade gastroenteropancreatic neuroendocrine neoplasms (HG GEP-NEN) typically disseminate early. Treatment of metastatic disease has limited benefit and prognosis is generally discouraging. Data on the clinical impact of mutations in HG GEP-NEN are scarce. There is an unmet need for reliable biomarkers to predict treatment outcome and prognosis in metastatic HG GEP-NEN. Patients with metastatic HG GEP-NEN diagnosed at three centres were selected for KRAS-, BRAF mutation and microsatellite instability (MSI) analyses. Results were linked to treatment outcome and overall survival. After pathological re-evaluation, 83 patients met inclusion criteria: 77 (93%) GEP neuroendocrine carcinomas (NEC) and six (7%) GEP neuroendocrine tumours (NET) G3. NEC harboured higher frequency of mutations than NET G3. Colon NEC harboured a particular high frequency of BRAF mutations (63%). Immediate disease progression on first-line chemotherapy was significantly higher for NEC with BRAF mutation (73%) versus wild-type (27%) (p = .016) and for colonic primary (65%) versus other NEC (28%) (p = .011). Colon NEC had a significant shorter PFS compared to other primary sites, a finding independent of BRAF status. Immediate disease progression was particularly frequent for BRAF mutated colon NEC (OR 10.2, p = .007). Surprisingly, BRAF mutation did not influence overall survival. KRAS mutation was associated with inferior overall survival for the whole NEC population (HR 2.02, p = .015), but not for those given first-line chemotherapy. All long-term survivors (>24 m) were double wild-type. Three NEC cases (4.8%) were MSI. Colon NEC with BRAF mutation predicted immediate disease progression on first-line chemotherapy, but did not affect PFS or OS. Benefit of first-line platinum/etoposide treatment seems limited for colon NEC, especially for BRAF mutated cases. KRAS mutations did not influence treatment efficacy nor survival for patients receiving first-line chemotherapy. Both frequency and clinical impact of KRAS/BRAF mutations in digestive NEC differ from prior results on digestive adenocarcinoma.

PURPOSE Gastroenteropancreatic neuroendocrine carcinomas (GEP-NEC) are rare and have a poor prognosis. Most GEP-NEC are diagnosed with metastatic disease, with only minor biopsies available for molecular diagnostics. We assessed the applicability of liquid biopsies for molecular profiling of GEP-NEC. MATERIALS AND METHODS We performed massive parallel sequencing of 76 cancer-related genes in circulating tumor DNA from 50 patients with advanced GEP-NEC and compared findings to previous analyses of solid tumor biopsies from the same patients. Plasma samples were collected before therapy, and the median time span between blood and tissue sampling was 25 days. RESULTS We detected 178 somatic mutations in the liquid biopsies, 127 (71%) were also detected in the solid biopsies, whereas 51 (29%) were unique to the liquid biopsies. In the same 76 genes, we previously detected 199 somatic mutations (single nucleotide variants) in solid biopsies, of which 127 (64%) were also now detected in liquid biopsies. In exploratory subgroup assessments, concordance was higher in patients with liver metastases ( P = 1.5 × 10–5) and increasing with level of liver involvement ( P = 1.2 × 10–4). The concordance was similar between GEP-NEC with different primary sites, except being lower in esophageal cases ( P = .001). Concordance was not associated with tumor mutation burden. Tumor tissue mutations also detected in liquid biopsies was lower for MSI (40%) versus MSS tumors (70%; P = 7.8 × 10–4). We identified potentially targetable mutations in plasma of 26 (52%) of patients with GEP-NEC; nine patients (18%) had potentially targetable mutation detected only in liquid biopsies. CONCLUSION Liquid biopsy analyses may be an applicable alternative to solid biopsies in GEP-NEC. Liquid biopsies may add additional mutations compared with tumor biopsies alone and could be useful for biomarker assessment in clinical trials for these patients.