Use of Imatinib Mesylate in Gastrointestinal Stromal Tumours: Pan-Birmingham Cancer Network Experience

Abstract

Aims Imatinib mesylate, a selective tyrosine kinase receptor inhibitor of KIT and PDGFRα, is currently licensed for the treatment of unresectable or metastatic gastrointestinal stromal tumours (GISTs), which are KIT positive. Partial response rates in 65% of patients and stable disease in 20% of patients are typically seen. The aim of this study was to assess the effectiveness and toxicity of an unselected cohort of patients treated with imatinib mesylate and to compare these results with published data. Materials and methods A retrospective audit of the use of imatinib mesylate in GISTs within the Pan-Birmingham Cancer Network was carried out. In total, 39 patients were identified, the first commenced imatinib mesylate in September 2001. Results The most common primary tumour sites were small intestine (19 [49%]) and stomach (12 [31%]). Initial curative resection was carried out in 21 (54%), palliative resection in three (8%) and 15 (38%) were unresectable. Of those who had curative resection, the median time to recurrence was 13 months (range 2–276). Common sites of metastases were liver (19 [49%]) and peritoneum (12 [31%]). At 24 months 70% remained on imatinib. A partial response was reported in 23 (59%), stable disease in seven (18%) and disease progression in four (10%). Five patients (13%) have yet to be reassessed at 3 months. Imatinib was well tolerated with minor side-effects; peri-orbital oedema (nine [23%]), skin rash (four [10%]), minor gastrointestinal bleed (one [3%]). No significant toxicity was documented in 18 (46%). Conclusions The response rates achieved in this unselected cohort of patients are consistent with published data. The duration of tumour control is good, with most patients responding to imatinib mesylate for more than 2 years. Side-effects are mild and acceptable.