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

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.

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.

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.

Neoadjuvant imatinib treatment for 6-9 months is a promising treatment for large gastric GISTs, allowing a high R0 resection rate with acceptable toxicity.