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Imatinib and inoperable or metastatic gastrointestinal stromal tumours. Longer follow-up confirms the overall survival benefit.

In 2002, patients with inoperable or metastatic gastrointestinal stromal tumours had a median overall survival time of about 19 months with available treatment options. When it was first marketed in this setting in 2002, the efficacy of imatinib, a tyrosine kinase inhibitor, was mainly based on one trial evaluating a surrogate endpoint. This review examines new data, focusing on overall survival. Longer-term data have been published for 56 patients enrolled in a trial comparing imatinib doses of 400 mg and 600 mg per day. The median overall survival time was 57 months and the median progression-free survival time was about 24 months, with no statistically significant difference between the two doses. Two randomised unblinded trials with similar designs compared imatinib doses of 400 mg and 800 mg/day in a total of more than 1600 patients. Combined analysis of the two trials showed no statistically significant difference in median overall survival between the two doses (48.8 months). In contrast, median progression-free survival was significantly longer with the higher dose, by about 4 months. Another trial compared continued treatment versus imatinib withdrawal after a year of treatment in patients whose tumour had stabilised on imatinib 400 mg/day. Imatinib withdrawal was associated with a higher risk of progression. However, when treatment was resumed at a dose of 400 mg/day after disease progression in 26 patients, the median overall survival time was similar to that in patients receiving continuous treatment. Initially, clinical evaluation showed that imatinib provoked many adverse effects, some of which were potentially severe. Cases of heart failure, secondary malignancies, bone remodelling and hepatic and ovarian disorders have since been reported. In the two trials comparing daily imatinib doses of 400 mg and 800 mg, about half of the patients experienced a serious adverse effect. The frequency of serious adverse effects was significantly higher with a daily dose of 800 mg than with 400 mg. The mortality rate was higher with imatinib 800 mg/day. In practice, compared with cytotoxic chemotherapy, imatinib provides a tangible overall survival benefit in patients with inoperable or metastatic gastrointestinal stromal tumours, at a cost of varied, frequent and potentially life-threatening adverse effects.