260 Molecular Profiling Contributes to Improved Outcomes Following Gastric GIST Resection: A Fifteen-Year Experience from a Specialist Centre

Abstract Aim GISTs are rare mesenchymal tumours with limited long-term outcome data. Surgery remains the only curative treatment option for localised gastric GISTs. We present the data from localised GISTs undergoing resection at our centre. Method Data was reviewed from the prospectively collated Cambridge-GIST database from 2010-2024. Only patients with localised gastric-GIST undergoing curative resection were included. Results 128 patients were included (Male=52.3%; Female=47.7%; median age 65.5years). Median GIST size was 5.5cm, and locations included: body (20.8%), greater curve (19.2%), lesser curve (22.4%), fundus (20.9%), cardia/GOJ (6.4%), and antrum/pylorus (8.8%). KIT mutations were found in 55% and PDGFRA in 24%. Proximal (fundus/cardia/GOJ) GISTs were predominantly KIT mutant (27/36=75%) and distal (pre-pyloric/antrum) were PDGFRA mutant (7/11=64%) (p<0.0001). Use of mutational analysis increased from 85.4% to 100% (p<0.0001) and imatinib therapy from 16.9% to 35.8% (p = 0.0002) between the first and second half of the period. Surgery was laparoscopic in 58% and open in 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 100% of known resections were R0. Complication rates were low (Clavien-Dindo grade ≥3 = 4.7%). There were no 30-day deaths, and 5-year disease-specific survival was 99%. Recurrence rates were low: 1.6% local and 7.8% distant. 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 suggest that surgical follow-up after curative surgery can be rationalised and patients reassured.