P-0140 - Experience of Managing Patients with Metastatic Gastrointestinal Stromal Tumour with Imatinib Mesylate at an Indian Centre

Abstract

Background: Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. Most commonly originate in the stomach and small intestine. Historically, these lesions were classified as leiomyomas or leiomyosarcomas. They are submucosal lesions, which grow endophytically in parallel with the lumen. One third of high risk, malignant GIST have poor prognosis after surgery. Imatinib mesylate is a KIT tyrosine kinase inhibitor with effect on metastatic GIST. About 80% of patients with GIST would experience tumor recurrence or metastasis after radical resection. The most common site of the metastasis is the liver. We report our long term follow up in patients with metastatic GIST receiving Imatinib. Methods: Retrospective analysis of patients diagnosed with metastatic GIST from 2004 to 2012 at our centre, who received Imatinib mesylate at an dose of 400 mg per day over 6 months. Patients profile, tumor response, side effects, time to progression and survival were evaluated. Results: Ten C-Kit or CD 117 positive GIST patients were enrolled at our centre, there were 8 (80%) male and 2 (20%) female. Median age of patients was 64 years (range 38 to 86 years). Five GISTs originated from stomach, 3 from rectum, 1 each from jejunum & ileum. Most common symptoms were anaemia and pain abdomen. Liver metastasis in 6, lung in 3 and breast in 1. Five patients underwent surgical treatment. Majority of them (80%) were of the high-risk malignant category. All of them started on Imatinib, all had palliative benefit, half had significant shrinkage of tumour mass. Most common side effects were periorbital oedema, muscle cramps, and diarrhea. Histologically, the majority had a pure spindle cell morphology. Follow-up of 5 cases, treated with adjuvant Imatinib for 6 months after surgical resection showed stable disease for periods from 5 to 8 years. However, 3 cases treated with Imatinib for longer than 6 months had problems due to recurrent, metastatic, or inoperable disease. The long-term Imatinib mesylate treatment was safe and well tolerated. At a median follow-up of 48 months (range 15 to 112 months), the 5 year survival rate was 88%. Conclusion: Adjuvant therapy Imatinib should be used for patients with high-risk advanced GISTs. The Imatinib mesylate treatment can prolong the survival of the patients who have metastatic GIST before or after radical surgery without toxicity of chemotherapy.