Background: Neuroendocrine tumours (NET) of the pancreas (PNET) or small bowel (SBNET) frequently present with metastases at initial diagnosis, undermining the efficacy of surgical treatment. Peptide receptor radionuclide therapy (PRRT) with radiolabelled somatostatin analogues, ⁹⁰Y-DOTATOC and ¹⁷⁷Lu-DOTATATE, has been shown to achieve prolonged progression-free survival (PFS) in a substantial number of non-surgical patients with advanced NET. Our aim was to prospectively determine the efficacy of a combination of radical loco-regional surgery and PRRT in patients with metastasised NET. Methods: A set of inclusion criteria was defined (e.g. G1/G2 NET, initial tumour diagnosis, treatment naïve patient, stage IV NET, positivity on 68Ga DOTA- PET/CT, eligibility for surgery and PRRT). Patients underwent PRRT within 3 months following surgery. Follow-up included biochemistry and imaging. In a sub-cohort, blood-based neuroendocrine gene transcript analysis of 51 genes (NETest) was used to define the effectiveness of treatment. Outcome measures included 5-year overall survival (OS) and PFS from initial diagnosis. Results: Twenty-five patients (5 PNET, 20 SBNET) met eligibility criteria and were included. There were 13 men (52%) and mean age was 57.1 years. All patients with SB NET underwent right hemicolectomy, terminal ileal resection and mesenteric lympadenectomy. In all PNET patients only limited pancreatic resection was required. The median number of PRRT cycles was 4 (range 2-6). Post-treatment mortality was 0%. Surgical morbidity was 12% (all Clavien-Dindo grade 1). Transient grade 1 toxicity occurred post-PRRT in 40%. NETest scores were increased in 8 patients (100%) pre-operatively and decreased in all following treatment. NETest decreases correlated with diminished tumour volume (R²=0.37, p=0.02). Median follow-up was 48 months (range 12-72months). Five-year OS was 90% and 5-year PFS was 84.3%. Conclusions: Radical loco-regional surgery for primary tumours combined with PRRT provides a novel, highly efficacious approach in metastasised NET. The NETest accurately measures the effectiveness of treatment.