Approximately 5% of gastrointestinal stromal tumors (GISTs) originate in the rectum, and historically, radical resection was commonly performed. Little is known about the outcome for rectal GIST in the era of imatinib.

Using a prospectively maintained database, this study retrospectively analyzed 47 localized primary rectal GISTs treated at our center from 1982 to 2016, stratified by when imatinib became available in 2000. Overall survival (OS), disease-specific survival (DSS), and recurrence-free survival (RFS) were analyzed by the Kaplan–Meier method.

Rectal GISTs represented 7.1% of 663 primary GISTs. The findings showed 17 patients in the pre-imatinib era and 30 patients in the imatinib era. The two groups had similar follow-up evaluation, age, gender, Miettinen risk, and distance to the anal verge. In the imatinib era, tumors were smaller at diagnosis (median 4 vs. 5 cm; p = 0.029), and 24 of the 30 patients received perioperative imatinib. In the high-risk patients, organ preservation and negative margins were more common among the 13 patients treated with neoadjuvant imatinib than among the 21 patients treated directly with surgery. High-risk patients who received perioperative imatinib (n = 15) had greater (or nearly significantly greater) 5-year OS, DSS, local RFS, and distant RFS than those who did not (n = 19) (91, 100, 100, and 71% vs. 47, 65, 74, and 41%; p = 0.049, 0.052, 0.077, 0.051, respectively). In the imatinib era, no patient has had a local recurrence or death due to GIST.

The use of imatinib is associated with organ preservation and improved oncologic outcome for patients with rectal GIST.