OBJECTIVETo evaluate the feasibility of imatinib reintroduction in gastrointestinal stromal tumor(GIST) with high recurrence risk after imatinib adjuvant therapy failure.

METHODSClinical and follow-up data of 24 recurrent GIST patients with high recurrence risk receiving imatinib standard dose reintroduction(400 mg/d or 600 mg/d) after stopping imatinib adjuvant treatment more than 3 months in Department of GI Oncology of Peking University Cancer Hospital from August 2005 to January 2016 were retrospectively analyzed. The objective response rate(ORR), relapse-free survival(RFS) of imatinib reintroduction were evaluated and the difference of efficacy in patients receiving different imatinib adjuvant therapy duration were compared.

RESULTSOf 24 patients, 21 were male and 3 were female. The median age was 53 years(39-72 years). Mutation detection of tumor tissues before imatinib therapy showed 20 patients had c-Kit exon 11 mutation,3 patients exon 9 mutation and 1 patient c-Kit/PDGFRA wild type mutation. The median recurrence time was 14 months in all the patients (95%CI:7.9-20.0) and in those patients receiving imatinib adjuvant therapy for 1 or 2 years (9 patients in each group, 95%CI:11.1-16.9 and 8.2-19.8 respectively). The median recurrence time of 3 patients receiving imatinib adjuvant therapy for 3 years was 24, 41 and 54 months respectively. Of 2 patients receiving imatinib adjuvant therapy for 5 years, the median recurrence time was 4 and 18 months. Only one patient received imatinib adjuvant therapy for 6 years, and the recurrence time was 6 months. Twenty patients with exon 11 mutation and 1 patient with wide type received imatinib treatment at a dose of 400 mg daily, and 3 patients with exon 9 mutation received the dosage of 600 mg per day. Among the patients receiving imatinib reintroduction, 11 patients(45.8%) got partial response(PR), 12 patients(50.0%) had stable disease and 1 patient had progression disease. The response rate in patients receiving imatinib adjuvant therapy for 1 year(6/9, 67%) was significantly higher than that in patients receiving adjuvant therapy for ≥2 years(3/15, 20%)(P=0.036). The median progression-free survival (PFS) of imatinib reintroduction was 31 months in all the patients(95%CI:23.6-38.4). The median PFS in patients receiving imatinib adjuvant therapy for 1 year(9 cases), 2 years (9 cases) and ≥3 years (6 cases) was 50 months(95%CI:27.3-72.7), 26 months(95%CI:10.7-41.3) and fall short of median PFS. No significant difference was observed among three groups(P=0.295).

CONCLUSIONSImatinib reintroduction is still effective to GIST after imatinib adjuvant therapy failure. The different imatinib adjuvant therapy duration can influence the benefit of imatinib reintroduction.