A randomised phase 2 study of continuous or intermittent dosing schedule of imatinib re-challenge in patients with tyrosine kinase inhibitor-refractory gastrointestinal stromal tumours

Background Imatinib re-challenge is one of the available therapeutic options for patients with treatment-refractory gastrointestinal stromal tumours (GIST). Intermittent dosing of imatinib was suggested to delay outgrow of the imatinib-resistant clones in a preclinical study, and it could potentially reduce the adverse events. Methods A randomised phase 2 study was performed to evaluate the efficacy and safety of a continuous or intermittent imatinib schedule in GIST patients whose disease had progressed to at least imatinib and sunitinib. Results Fifty patients were included in the full analysis set. The disease control rate at 12 weeks was 34.8% and 43.5%, and median progression-free survival was 1.68 and 1.57 months in the continuous and intermittent groups, respectively. The frequency of diarrhoea, anorexia, decreased neutrophil, or dysphagia was lower in the intermittent group. The scores for global health status/quality of life was not significantly deteriorated over the 8 weeks in both groups. Conclusions The intermittent dosage did not improve the efficacy outcomes as compared to the continuous dosage, but showed slightly better safety profiles. Given the limited efficacy of imatinib re-challenge, intermittent dosage may also be considered in clinical circumstances where standard fourth-line agent is unavailable or all other viable treatments failed.