Phase II study of neoadjuvant imatinib in large gastrointestinal stromal tumours of the stomach

Background:Gastrointestinal stromal tumours (GISTs) with high-risk features have poor prognosis even if adjuvant treatment is given. Neoadjuvant imatinib may increase the cure rate by shrinking large GISTs and preserve organ function.Methods:We conducted an Asian multinational phase II study for patients with gastric GISTs ≥10 cm. Patients received neoadjuvant imatinib (400 mg/day) for 6-9 months. The primary end point was R0 resection rate.Results:A total of 56 patients were enroled in this study. In the full analysis set of 53 patients, neoadjuvant imatinib for ≥6 months was completed in 46 patients. Grade 3-4 neutropenia and rash occurred in 8% and 9%, respectively, but there were no treatment-related deaths. The response rate by RECIST was 62% (95% CI, 48-75%). The R0 resection rate was 91% (48/53) (95% CI, 79-97%). Preservation of at least half of the stomach was achieved in 42 of 48 patients with R0 resection. At the median follow-up time of 32 months, 2-year overall and progression-free survival rates were 98% and 89%, respectively.Conclusions:Neoadjuvant imatinib treatment for 6-9 months is a promising treatment for large gastric GISTs, allowing a high R0 resection rate with acceptable toxicity.