202 Long-term Outcomes of Gastric Gastrointestinal Stromal Tumours (GIST) Following Surgical Resection: 15-year Experience from A Specialist Multidisciplinary Centre

Abstract Introduction GISTs are rare tumours arising from the interstitial cells of Cajal with an annual incidence of 10-15/million and limited data on long-term outcomes.We present the data from localised gastric-GISTs undergoing resection in our unit. Methods Data from the prospectively collated Cambridge-GIST database from 2010-2024 was reviewed. Only gastric-GIST patients with a curative resection were included in this analysis. Results There were 128 patients (male=52.3%;female=47.7%;median age=65.5years;range 26-84years). Median GIST size=5.5cm (0.5cm-40cm).GIST location was: body (20.8%), greater curve (19.2%), lesser curve(22.4%), fundus (20.9%), cardia/GOJ(6.4%) and pyloric/antrum(8.8%).Molecular phenotyping was: KIT=55%, PDGFRA=24%, SDH deficient=1%, unknown=20%.Proximal GISTs (fundus/cardia/GOJ) were predominantly KIT mutant (27/36=75%) compared to distal GISTs (pre-pyloric/antrum) that were predominantly PDGFRA mutant (7/11=64%)(p<0.0001).Between 2010-2017 and 2017-2024 there was an increase in mutational analysis (85.4% to 100%,p<0.0001) and neoadjuvant/adjuvant imatinib(16.9% to 35.8%p=0.0002).Operative approach was laparoscopic=57%, open=42%.90.6% of cases had a localised resection,3.9% distal gastrectomy and 5.5% total gastrectomy. The leak rate was 2.6% and 99% of resections were R0.No 30-day deaths and 2 non-GIST related 1-year deaths were observed. Local and distant recurrence rate was 1.6% and 7.8% respectively. The 5-year OS was 95%. Conclusions We report low local recurrence rates in our cohort and attribute this to the increasing use of molecular phenotyping and neo-adjuvant imatinib as per our MDT approach.Our data suggests that surgical follow-up following curative surgery can be rationalised and patients reassured.Further work is being undertaken to incorporate histological and molecular features to prognosticate all-comers with this rare cancer.