1758P - Real-world efficacy of imatinib in patients with advanced GIST: The LRG registry

Background

Imatinib (IM) has been the standard treatment for Gastrointestinal Stromal Tumors (GIST) for over two decades, showing a median progression-free survival (mPFS) of approximately two years in pivotal trials. We conducted an updated review of one of the largest registries to assess IM's real-world effectiveness in advanced/metastatic GIST patients, emphasizing molecular subtypes.

Methods

Life Raft Group (LRG) patient registry data including demographics, tumor locations, mutational status, and treatment history was reviewed.

Results

A total of 2,661 patients diagnosed with GIST were identified, of which 1,541 patients (57.9%) had known mutation status. We evaluated 798 advanced/metastatic GISTs by predicted IM sensitivity (see table). While in the whole cohort mPFS was 31.2 months (95% CI 27.6-36.7), the mPFS in the IM-sensitive cohort (n=559) was significantly higher at 42 months (95% CI 36.6 – 53.9) compared to 18.8 months (95% CI 10.9 – 29.5) in the IM-intermediate cohort (n=119) and 15 months (95% CI 10.0 – 22.1) in the IM-insensitive cohort (n=120). The median overall survival (mOS) in 533 advanced/metastatic KIT exon 11 patients was 12.6 years (95% CI 11.1-14.3). The rate of extra-abdominal metastasis in 364 advanced GIST patients with KIT/PDGFRA mutations and abdominal primaries was 17% (n=61), with 47 (13%) reporting thoracic metastasis and 28 (8%) reporting bone/spine metastasis. Only one patient reported a brain metastasis (0.2%). Table: 1758P

PFS and OS with 1st line IM

Conclusions

Our study shows that initial IM treatment may achieve a mPFS of over three years for IM-sensitive mutations, with a mOS >10 years. Additionally, 17% developed extra-abdominal metastases, mainly to the thorax and bones. This highlights the need to integrate mutation status and clinical-genomic data from large cohorts into GIST therapeutic development and clinical counseling.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The Life Raft Group.

Funding

Has not received any funding.

Disclosure

J. Call, D. Evans, S. Rothschild: Financial Interests, Institutional, Other, Sponsor/Funding and Educational Grants: Blueprint, Cogent Biosciences, Daiichi Sankyo, Deciphera, Genentech, IDRx, Novartis, Pfizer, Theseus. All other authors have declared no conflicts of interest.