Frequent rectal gastrointestinal stromal tumor recurrences in the imatinib era: Retrospective analysis of an International Patient Registry

Introduction Rectal gastrointestinal stromal tumor (GIST) is rare and comprises about 3% of GIST. Methods Registry data was collected by the Life Raft Group June 1976 to November 2017. All patients had a histologic GIST diagnosis. Demographic, clinicopathologic, and clinical outcome data were patient reported. Recurrence‐free survival (RFS) was analyzed using the Kaplan‐Meier method and Cox regression analysis. Results Of 1798 patients in the database, 48 had localized rectal GIST (2.7%). Patients were frequently male (58.3%) and non‐Hispanic whites (58.3%). Median age at diagnosis was 52 years. Most patients (77%) were diagnosed in the imatinib era (2001 to current). Over half (54.2%) of the cohort had mutation testing and all profiled tumors possessed KIT mutations (exon 9: 7.7%, exon 11: 88.5%, and exon 13: 3.8%). Most evaluable patients (26/28; 92.9%) had high‐risk disease (modified NIH criteria) and nearly all patients (95.8%) received imatinib. Median follow‐up was 8.8 years (range, 0.3‐30.7) and overall RFS was 8.0 years (95% CI, 2.9‐13.1). Thirty‐two percent (12/37) of patients in the post‐imatinib era developed recurrent disease. Diagnosis in the imatinib era was associated with improved RFS (HR = 0.22, 95% CI, 0.08‐0.62; P = .004) in the multivariable model. Conclusion We find that disease recurrence remains prevalent in one‐third of patients treated during the imatinib‐era.