P-0153 - Imatinib Mesylate in Treatment of Advanced GIST – Single Institution Experience

Abstract

Introduction: Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract, representing 1-2% of all gastrointestinal malignancies. Imatinib mesylate is an inhibitor of the tyrosine kinase receptor and standard of care for treatment of metastatic or unresectable GIST. Due to reimbursement limits of our National Health System, currently imatinib used in a dose 400 mg/day is our only treatment option for advanced GIST. Our aim was to assess the efficacy and tolerability of imatinib in our daily practice. Methods: We have retrospectively analyzed data of patients with unresectable or metastatic GIST, treated from 2004 to 2013, with Imatinib mesylate 400 mg/day. The treatment outcomes as well as safety profile were evaluated. Adverse events were assessed in accordance with the National Cancer Institute Common Toxicity Criteria. Response Evaluation in Solid Tumors (RECIST) Criteria was used for estimating the tumor response rate. Results: A total of 51 patients with unresectable or metastatic GIST were identified, of which 45% were males and 55% females. 23 patients are still under treatment and 28 patients have died. Median age 62 (range 17-84). Treatment outcomes included complete response in 2(3,92%) patients, partial response in 14(27,45%), stable disease in 30(58,82%), and primary resistant in 5(9,8%) patients. The median progression-free survival was 28 months (range, 1-90). The median overall survival (OS) was 32 months (range 1,7-96). Following grade 3 or 4 adverse events were observed: anemia (13,5%), renal dysfunction (5%), hypoglycemia (2%), diarrhea (2%). Conclusion: Imatinib is a drug of great importance in treating GIST patents due to high efficacy, good toxicity profile and convenient usage. Our results have demonstrated good PFS as well as OS. However, a small difference between median PFS and OS, emphasizes need for second line therapy or dose escalation. The therapy was well tolerated and majority of serious adverse events were disease related and not caused by the treatment.