Long-Term Follow-Up Outcome of Imatinib Mesylate Treatment for Recurrent and Unresectable Gastrointestinal Stromal Tumors

Background: The follow-up study of up to 71 months of a randomized phase II B2222 trial has demonstrated a long-term survival in patients with recurrent or unresectable gastrointestinal stromal tumors (GISTs). One subset of the patients (17.7%) has been alive for over 9 years with continuous imatinib mesylate (imatinib) treatment. Here, we report the retrospective analysis of recurrent or unresectable GIST patients with imatinib treatment at our institution. Methods: We summarized the data of 20 patients with recurrent or unresectable GIST treated with imatinib. Results: Patients were followed for a median of 40 months (range 2.5–103) under imatinib treatment. The median progression-free survival (PFS) was 89 months and overall survival for 8 years was 67%. Fifteen patients showed continuous partial response or stable disease with imatinib treatment. The median PFS was 45 months and the median size of the primary tumor was 7.6 cm (range 2.8–18). Four patients showed progressive disease. The median PFS was 56 months and the median size of the primary tumor was 11.9 cm (range 6.7–19). Grade 3 or 4 adverse events occurred in neutropenia (10%), anemia (15%) and renal dysfunction (5%). However, all patients were well managed by supportive treatment and none were discontinued from imatinib treatment due to toxicity or adverse events. Conclusion: Imatinib had a high efficacy in patients with unresectable and recurrent GIST during long-term follow-up. All patients were well managed by supportive treatment against adverse events and they were able to take imatinib without discontinuation. The management of adverse events was a key factor for achieving a long-term survival. In addition, the potential risk of imatinib-resistant GISTs tends to depend on the size of the primary GISTs.