BRAFV600E mutation: A promising target in colorectal neuroendocrine carcinoma.

To determine the role of BRAFV600E mutation and MAPK signaling as well as the effects of BRAF and MEK directed therapy in gastroenteropancreatic neuroendocrine neoplasia (GEP-NEN), with a focus on highly aggressive gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC). Using Sanger sequencing of BRAF exon 15 we determined the frequency of BRAFV600E mutations in 71 primary GEP-NENs. MEK phosphorylation was examined by immunohistochemistry in corresponding tissue samples. To evaluate the biological relevance of BRAFV600E mutation and MAPK signaling in GEP-NECs, effects of a pharmacological BRAF and MEK inhibition were analyzed in NEC cell lines both in vitro and in vivo. BRAFV600E mutation was detected in 9.9% of all GEP-NENs. Interestingly, only NECs of the colon harbored BRAFV600E mutations, leading to a mutation frequency of 46.7% in this subgroup of patients. In addition, a BRAFV600E mutation was significantly associated with high levels of MEK phosphorylation (pMEK) and advanced tumor stages. Pharmacological inhibition of BRAF and MEK abrogated NEC cell growth, inducing G1 cell cycle arrest and apoptosis only in BRAFV600E mutated cells. BRAF inhibitor dabrafenib and MEK inhibitor trametinib prevented growth of BRAFV600E positive NEC xenografts. High frequencies of BRAFV600E mutation and elevated expression levels of pMEK were detected in biologically aggressive and highly proliferative colorectal NECs. We provide evidence that targeting BRAF oncogene may represent a therapeutic strategy for patients with BRAF mutant colorectal NECs.

Investigation of receptor radionuclide therapy with 177Lu-DOTATATE in patients with GEP-NEN and a high Ki-67 proliferation index.

PURPOSE: In the 2010 WHO classification, a Ki-67 proliferation index of 20% is the cut-off between intermediate-grade and high-grade gastroenteropancreatic neuroendocrine neoplasia (GEP-NEN). However, in clinical practice, tumours with a Ki-67 index of >15% are often considered high grade and treated with chemotherapy. In 40-70% of high-grade NENs, somatostatin receptors are overexpressed, enabling peptide receptor radionuclide therapy (PRRT) to be performed. We investigated the role of PRRT with 177Lu-DOTATATE in patients with GEP-NEN and a high Ki-67 proliferation index. METHODS: A total of 33 patients with advanced GEP-NENs, positive somatostatin receptor imaging (SRI+) and a Ki-67 proliferation index ranging from 15% to 70% were treated with Lu-PRRT. A cumulative activity of 18.5 GBq or 27.8 GBq of 177Lu-DOTATATE was administered in four or five cycles. Receiver operating characteristic (ROC) curve analysis was used to determine the best threshold of Ki-67 expression to predict disease progression. RESULTS: All patients completed the intended treatment. The median follow-up was 43 months (range 3-69 months). Two patients (6%) achieved a partial response and 21 (64%) showed stable disease, giving a disease control rate (DCR) of 70%. The median progression-free survival (PFS) was 23 months (95% CI 14.9-31.0 months) and the median overall survival was 52.9 months (95% CI 17.1-68.9 months). ROC curve analysis at 23 months revealed that the best Ki-67 index cut-off was 35%. In 23 patients (70%) the Ki-67 index was ≤35% and in 10 patients (30%) the Ki-67 index was in the range 36-70%. The DCR in the former group was 87% and 30% in the latter. The median PFS was 26.3 months (95% CI 18.4-37.7 months) and 6.8 months (95% CI 2.1-27 months), respectively (p = 0.005). CONCLUSIONS: Lu-PRRT showed antitumour activity in SRI+ GEP-NENs of intermediate and high-grade. DCR and PFS were significantly better in patients with a Ki-67 index of ≤35% than in those with a Ki-67 index of >35%. On the basis of these results, PRRT should be considered as a therapeutic option in patients with high-grade SRI+ GEP-NENs, in particular those with a Ki-67 proliferation index of ≤35%.

Development and validation of a nomogram to predict overall survival of gastroenteropancreatic neuroendocrine carcinoma: a SEER database analysis.

Background: Gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC) is a rare group of diseases with poor prognosis and the assessment of its prognosis is a significant challenge. This study aimed to develop and validate a prognostic nomogram to assess overall survival (OS) in patients with GEP-NEC. Methods: Patients diagnosed with poorly differentiated GEP-NEC were collected from the Surveillance, Epidemiology, and End Results (SEER) database between 2011 and 2015 and were randomly assigned to the training or validation cohort in a 7:3 ratio. The data included details of clinicopathological characteristics, therapeutic interventions and survival outcomes. Univariate and multivariate Cox regression analyses were used to identify independent prognostic factors. Nomogram was used to predict OS at 1 and 2 years. The nomogram was internally validated with validation cohort, and its predictive ability was evaluated using concordance index (C-index), receiver operating characteristic (ROC) curves, calibration plots, decision curve analysis (DCA), and integrated discrimination improvement (IDI) index. Results: A total of 887 patients were divided into the training group (n=623) and the validation group (n=264). A total of 476 patients (53.66%) were in stage IV. Based on multivariate analysis, a nomogram was constructed with age, gender, N stage, tumor size, primary tumor resection, radiotherapy and chemotherapy (P<0.05). The C-index was 0.701 [95% confidential interval (CI): 0.677-0.725] and 0.731 (95% CI: 0.698-0.764) for the training and validation groups, respectively. The C-index, ROC, IDI and DCA results indicated that this nomogram model has a good predictive value. Conclusions: In this study, a nomogram model based on seven independent prognostic factors provided visualization of the risk and could help clinicians predict the 1-year and 2-year OS for GEP-NEC. This tool can provide personalized survival predictions and improve clinical decision making for the management of GEP-NEC.

Patient-Derived Organoid Models of Human Neuroendocrine Carcinoma.

Gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC) is a poorly understood disease with limited treatment options. A better understanding of this disease would greatly benefit from the availability of representative preclinical models. Here, we present the potential of tumor organoids, three-dimensional cultures of tumor cells, to model GEP-NEC. We established three GEP-NEC organoid lines, originating from the stomach and colon, and characterized them using DNA sequencing and immunohistochemistry. Organoids largely resembled the original tumor in expression of synaptophysin, chromogranin and Ki-67. Models derived from tumors containing both neuroendocrine and non-neuroendocrine components were at risk of overgrowth by non-neuroendocrine tumor cells. Organoids were derived from patients treated with cisplatin and everolimus and for the three patients studied, organoid chemosensitivity paralleled clinical response. We demonstrate the feasibility of establishing NEC organoid lines and their potential applications. Organoid culture has the potential to greatly extend the repertoire of preclinical models for GEP-NEC, supporting drug development for this difficult-to-treat tumor type.

The impact of primary tumor site on outcomes of treatment with etoposide and cisplatin in grade 3 gastroenteropancreatic neuroendocrine carcinoma.

Background: Gastroenteropancreatic neuroendocrine carcinoma (GEP-NEC) is a heterogeneous disease in terms of embryonic origin, aggressiveness, prognosis, and genomic profiling. Data regarding the efficacy of etoposide and cisplatin (EP) as a standard treatment of the primary tumor site in GEP-NEC are limited. Materials and Methods: We analyzed 64 patients with histopathologically confirmed metastatic GEP-NEC who received EP at Samsung Medical Center, Seoul, Korea, between January 2010 and January 2018. Based on primary tumor site, outcome of treatment with EP was evaluated. Results: Primary sites included 22 foregut-derived GEP-NECs (stomach, n = 6; duodenum, n = 4; pancreas, n = 12), 4 midgut-derived GEP-NECs, 5 hindgut-derived GEP-NECs of the rectum, 25 GEP-NECs originating from the hepatobiliary (HB) tract, and 12 GEP-NECs involving only intra-abdominal lymph nodes. No patient had a complete response (CR) and 17 had a partial response (PR), resulting in a 27.9% response rate (RR). When evaluating the efficacy of EP based on primary tumor site, the RR was most favorable in GEP-NECs involving only intra-abdominal lymph nodes, followed by GEP-NECs originating from foregut, midgut, HB, and hindgut. However, no statistically significant difference was observed for RR based on primary tumor site (P = 0.821). Similarly, no significant differences were found for progression-free survival (PFS) among patients with GEP-NECs arising from various primary tumor sites. Conclusion: Results from this study showed that RR and PFS associated with EP treatment were not different based on the primary tumor site in patients with advanced or metastatic GEP-NEC.

The impact of pathologic differentiation (well/poorly) and the degree of Ki-67 index in patients with metastatic WHO grade 3 GEP-NECs.

We investigated the impact of pathologic differentiation (well or poorly differentiated) in metastatic grade 3 GEP-NEC patients receiving etoposide and platinum (EP)-based therapy, and evaluated a more exact Ki67 index cut-off point to select patients with grade 3 GEP-NEC who might benefit from EP-based therapy. A total of 31 patients with metastatic grade 3 GEP-NECs receiving EP-based therapy were included in this study. Primary sites included 13 foregut-derived GEP-NECs [stomach (n = 4), duodenum (n = 4), and pancreas (n = 5)] and 2 hindgut-derived GEP-NECs of the rectum. 14 patients had well differentiated (WD) and 17 had poorly differentiated (PD). Between WD and PD grade 3 GEP-NECs, there was a significant difference in the distribution of Ki67 index. There was no significant difference of treatment efficacy between WD and PD grade 3 GEP-NECs (RR; 35.7% vs. 41.2%, p = 0.525). Tumor response to EP occurred in 5 of 7 patients with Ki67 > 60% and 7 of 24 with Ki67 ≤ 60%, which was significantly different (RR; 71.4% vs. 29.2%, P = 0.043). Among grade 3 GEP-NECs, there was a significant difference in ranges of Ki67 index between WD and PD NECs. Higher levels (> 60%) of Ki67 index might be a predictive marker for efficacy of EP as a standard regimen in grade 3 GEP-NECs.