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Patients with extrapulmonary poorly differentiated neuroendocrine carcinomas (EP-PD-NECs) have a poor prognosis. Surgery is offered for those with localised disease, but the majority of patients present with advanced disease. Treatment strategies adopted are analogous to that of high grade NECs of the lung, with platinum/etoposide-based regimens advocated in the first-line setting for advanced disease. There is no standard second-line therapy. Research into their molecular and immune pathways may pave the way for novel drug discovery. The molecular drivers of NEC are best identified in small cell lung carcinoma, which present with near universal genomic alterations in TP53 and RB1. The genetics of EP-PD-NEC remain poorly understood; TP53, KRAS, PIK3CA/PTEN and BRAF mutations have been identified, with alterations in the BRCA pathway reported additionally in small cell NEC of the cervix and absence of argininosuccinate synthetase 1 expression in NEC of the urinary bladder. The use of cell lines and patient-derived xenografts (PDX) to predict response to treatment in NEC and the emergence of alternative biomarkers, such as circulating tumour cells and cell-free DNA, will also be explored. Despite limited published data on the immune microenvironment of EP-NEC, there are a number of clinical trials investigating the use of immune-targeted agents in this disease category, with conflicting emerging data from studies thus far. This review will summarise the treatment and available molecular and immune data in this under researched diagnosis and may stimulate the direction of future exploratory studies.

The choice of first-line treatment for metastatic pancreatic neuroendocrine tumors (mP-NET) is mainly based on prognostic factors. ENETS-2016 guidelines stratified treatment according to 3 groups: Group 1, patients in whom all lesions could be removed; Group 2, patients with Ki67 <10%, low tumor burden, no symptoms and stable disease, for whom a watch-and-wait strategy or somatostatin analogs are proposed; Group 3, symptomatic patients or with Ki67 >10% or significant tumor burden or progressive disease, for whom a systemic chemotherapy is proposed. This retrospective study aimed to determine patient distribution, characteristics and outcome among these 3 groups. Patients with mP-NET diagnosis from 2004 to 2016 were categorized into the three groups. Prognosis was calculated using the Kaplan–Meier method. All treatments were recorded, and consistency with ENETS guidelines was explored. 104 patients were analyzed: 64% synchronous mP-NET, 80% grade 2 tumors and median overall survival (OS) of 104 (95% CI: 65–143) months. There were 15 patients in ENETS Group 1, 16 in Group 2 and 73 in Group 3. Median OS was not reached in Groups 1 and 2 and was 64 months (35–93) in Group 3. High liver tumor volume, high-grade tumor and progressive disease were associated with worse OS in multivariate analysis. The first-line treatment was in accordance with guidelines in 82%. 77% percent of deceased patients received less than 4 lines of treatment. Most patients are in Group 3 and do not receive all available treatments. Thus, trials are warranted to improve first-line chemotherapy. Alternative treatments may be considered for less aggressive disease.

A rechallenge is common after the initial efficacy of alkylating-based chemotherapy (ALK) in pancreatic neuroendocrine tumors (PanNET). High MGMT expression seems associated with a lower response to ALK. We aimed to evaluate the efficacy and toxicity of ALK rechallenge in PanNET, and to assess the evolution of MGMT expression under ALK. All consecutive patients with advanced PanNETs who received initial ALK (achieving tumor control) followed by a pause of > 3 months, then an ALK rechallenge (ALK2) upon progression were retrospectively studied (cohort A). The primary endpoint was progression-free survival under ALK2 (PFS2). The MGMT expression was retrospectively assessed by immunohistochemistry (H-score) in consecutive PanNET surgically resected following ALK (cohort B). We found that Cohort A included 62 patients (median Ki67 8%), for whom ALK1 followed by a pause achieved an objective response rate of 55% and a PFS1 of 23.7 months (95% IC, 19.8–27.6). ALK2 achieved no objective response and stability in 62% of patients. The median PFS2 was 9.2 months (IC 95% 7.1–11.3). At multivariable analysis, a hormonal syndrome (P = 0.032) and a pause longer than 12 months (P = 0.041) were associated with a longer PFS2. In cohort B (17 patients), the median MGMT H-score increased from 45 (IQR 18–105) before ALK to 100 (IQR 56–180) after ALK (P = 0.003). We conclude that after the initial efficacy of ALK treatment, a pause followed by ALK rechallenge might be appropriate to prolong tumor control, improve quality of life and limit long-term adverse events. Increased MGMT expression under ALK might explain the low efficacy of ALK rechallenge.