Introduction: The WHO classification distinguishes G3NET as a separate entity. Literature on G3NETs is limited to case-reports and small case-series. We aimed to characterise G3NETs from a large tertiary centre.
Methods: Retrospective analysis from NET database: 20122019. All referrals are discussed at a specialist NET-MDT before entry into clinical pathway. Core NET-MDT consists of a radiologist, nuclear-medicine radiologist, histopathologist, specialist-nurses, gastroenterologist, oncologist, endocrinologist, and liver surgeons. Imaging and biochemistry is performed every 6 months or as clinically indicated.
Results: 40 G3NETs were identified, with complete data available for 22 at the time of this abstract. Mean(S.D.) age was 69.18(11.1) years (6 females, 16 males). 36.3%(8/22) had undetectable primary, 13.6%(3/22) pancreatic, 13.6%(3/22) small bowel, remaining were colonic, gastric, lung and rectal primary tumours. Median: Ki67 30%, range: 2560% 12/16 had positive or equivocal somatostatin-receptor(SSR) status on imaging. 1 Rectal NET and 3 with undetectable primary had negative SSR imaging. Chromogrannin-A(CGA) and CGB were elevated in 18/22 different patients with mean(S.D.) of 644.592(592.80) pmol/l and 722.45(735.61) pmol/l respectively. Urine HIAA was elevated in 17/22 with mean(S.D.) of 819(813.23). 5/22 had normal levels of all tumor-markers (2 colonic, 1 rectal, 1 unknown and 1 pancreatic). 10/22 received Somatostatin-analogues(SSA): all SSR positive with at-least one elevated tumor-marker. There was no significant change in tumor-marker after SSA. 9/22 received chemotherapy (5/22 capecitabine+temazolamide, 3/22 carboplatin+etopiside, 1 everolimus, 1 FOLFIRI). 5/22 had both SSA & chemotherapy. 0 received PRRT. Of 16 deaths (69.5%), mean length of survival after referral was 15.6 months. Survival >6 months was associated with chemotherapy +/− SSA treatment.
Conclusion: Data from one of UKs largest specialist NET centres, show G3NETs have high mortality with variable tumor behaviour. G3NETs should be managed in specialist centres with NET-MDT expertise.