Background: Neuroendocrine carcinomas (NEC) are rare and aggressive cancers. There are no randomised trials to date to establish standard therapy for advanced G3 gastrointestinal (GI) NENs. Extrapolating from small cell lung cancer data, standard practice is to treat G3 GI-NENs with etoposide and carboplatin. Paclitaxel is also active in NECs however there is no data on the role of nab-paclitaxel. NABNEC (ANZCTR # 12616000958482) aimed to determine the activity, safety and tolerability of carboplatin and nab-paclitaxel in advanced G3 GI-NENs and to enhance our understanding of the biology and imaging characteristics of such NENs. Methods: NABNEC was designed as a randomised non-comparative phase II study, evaluating the activity of nab-paclitaxel in patients with advanced and/or metastatic non-resectable G3 GI-NENs. The statistical plan was that 46 evaluable patients in the experimental arm would give 80% power and 95% confidence to rule out a 30% RR in favour of a more interesting RR of 50% at 6 months. Protocol version 3.0 was amended and randomisation to the control arm was suspended after 12 patients. Primary endpoint was objective response rate (RR) by RECIST 1.1. Secondary endpoints were progression free survival, overall survival, adverse events by NCI-CTCAE V4.03 and quality of life (EORTC QLQC30, QLQ-GINET21 questionnaires). Translational research endpoints include blood and tissue biomarkers including circulating tumour cells profiling, mutation profile (whole exome sequencing) and DNA methylation profile correlated with clinical endpoints. Correlation of 18-fluoro-deoxyglucose positron emission tomography (FDG-PET) to early response has also been evaluated. Results: 60 patients were accrued between Sep 2016 and Dec 2021 from 16 centres, resulting in 58 evaluable patients, 12 (control arm), 46 (experimental arm). 43 patients (75%) had tumours with Ki-67>55%; the remainder had Ki-67 between 20 and 55%. About 20% had pancreatic primaries; more than half had liver metastases. The NABNEC trial met its primary endpoint. RR was 53% (38-69%) in the experimental treatment arm compared to 42% (16-71%) in the control group. Progression free survival was not different between the 2 treatments. 24m overall survival was 25% in the experimental group compared to 17% in the control. Grade 3 toxicity was worse in the nab-paclitaxel arms (52% v 42%). Quality of life and tertiary outcomes are being analysed. Conclusions: The combination of carboplatin and nab-paclitaxel is an active regimen for G3 GI-NENs. Further evaluation in a Phase III study is warranted. Clinical trial information: ACTRN12616000958482.