1513P Impact of mutational status on long-term treatment outcomes in patients with advanced gastrointestinal stromal tumors (GIST) treated in the first line with imatinib

GISTs are driven by genetic aberrations, mostly observed within KIT and PDGFRA genes. Standard first-line therapy for inoperable/metastatic GIST includes imatinib. The presence of specific alterations may impact imatinib efficacy patients' survival. We aimed to analyze the PDGFR mutation in patients with treated first line two cohorts according anatomical location. Prospectively collected data advanced known mutational status (KIT/PDGFRA) between 01/2001 12/2021 were analyzed. Survival analyses performed using Kaplan-Meier method log-rank test, while multivariate Cox regression was used identify factors associated progression-free survival (PFS) overall (OS). 344 (46.5% female, 35.8% gastric GIST) have been included. Frequency mutations presented table. With median follow-up 5.2years, PFS 40.6 (95%CI 32.8-48.5) months, OS 82.4 67.7-97.1) months. In analysis correlated longer were: female gender (HR 0.60; 95%CI 0.37-0.97) ex 11 point 0.22; 0.70-0.73), non-gastric GIST: codon 557-558 deletions 0.43; 0.24-0.75), 0.48; 0.27-0.87) or other 0.40; 0.23-0.70) no 18 D842V 0.11; 0.04-0.34). Only 0.41; 0.24-0.70) 0.32; 0.14-0.71), deletions/indels/duplications 0.57; 0.36-0.88) GIST.Table: 1513PDistribution aberrations patientsOverall (n=344) %Gastric (n=123) %Non-gastric (n=221) %pKIT exon wild-type32.033.331.20.003KIT codons deletion29.739.824KIT deletions, duplications, indels,23.517.127.1KIT mutations14.89.817.6KIT 9 wild-type87.298.481.0<0.001KIT 502-502 duplication12.81.619.0KIT than 111.20.81.4-PDGFRA wild-type95.390.298.3<0.001PDGFRA mutation3.56.51.8PDGFRA 842-847 indels1.23.30PDGFRA 180.30.80- Open table a new tab Mutational genes long-term different can serve as prognostic predictive factor.