Efficacy
In the initial phase II trial, updated long-term results demonstrated that at a median follow up of 63 months, median survival was 57 months for all patients, with no significant differences between the two dose groups (HR 0.873, p=0.5506). Mutational analyses was performed on 87% of patients, data demonstrated patients with KIT exon 11 mutation had a median OS 63 months, KIT exon 9 mutation median OS 44 months, other KIT mutations or no mutations had significant shorter median OS of 26 months.r
In the phase III trial, at a median follow up of 10.9 years, there was no significant difference in terms of PFS between 400 mg and 800 mg groups, with median PFS of 1.7 years in the lower dose group and 2.0 years in the higher dose group (HR 0.91 [0.79 – 1.04], p=0.18). There was no significant difference between the groups in terms of OS, with OS of 3.9 years in both treatment arms (HR 0.93 [0.80 – 1.07], p=.31). 10 year OS rates were 9.5% and 9.2% for the 400 mg and 800 mg arms respectively. Of 417 patients in the 400 mg group who had progressive disease, 196 crossed over to the 800 mg group at disease progression. A year after crossover, 17.4% of patients remained on the treatment. r
Kaplan-Meier curves PFS (A) & OS (B) phase III randomised trial comparing imatinib 400mg daily versus 800mg daily, showing no statistical benefit r
© J Clin Oncol 2017
Forest plot for interaction effect of KIT mutation status on treatment effect predicting (A) PFS and (B) OS r
© J Clin Oncol 2017