Treatment with imatinib appears to improve outcomes for patients with gastrointestinal stromal tumors (GISTs) with rectal tumors, according to a study published in BJS Open.

Patients with GISTs in the study who received neoadjuvant imatinib had a median 30% (range, 0 to -56%) reduction in tumor size prior to resection surgery. The reduction in size enabled the use of less-extensive resection surgery compared to the surgery planned using imaging prior to imatinib treatment with almost half of the patients receiving sphincter-preserving surgery (47.8%) compared to the initially planned 17.4%.

During the follow-up period, none of the 29 patients who received perioperative imatinib experienced recurrence compared to 1 out of the 5 patients who did not receive imatinib either before or after surgery.


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“Treatment with imatinib for rectal GISTs seems to improve outcomes, and neoadjuvant imatinib increases the rate of sphincter-preserving surgery,” the authors said.

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In addition to more patients receiving sphincter-preserving surgery, there was a reduction in planned abdominoperineal resection from 47.8% to 30.4% and total pelvic exenteration from 34.8% to 21.7% to achieve complete resection.

The patients in the study who received neoadjuvant imatinib (n=23) had significantly larger tumors than patients who received upfront surgical resection (n=11) without initial imatinib treatment (median 8.3 cm vs 2.5 cm; P =.01). The group of patients receiving neoadjuvant imatinib also included a larger percentage of high-risk patients based on the modified Fletcher classification system compared to those who received upfront surgery (87.0% vs 54.5%).

All but 5 patients achieved R0 margin status after surgery. Of these patients, 3 achieved R1 and 2 achieved R2 margins and all received neoadjuvant imatinib followed by adjuvant imatinib after surgery.

A total of 34 patients were identified from a single site for the study between July 2008 and February 2021. There were no significant differences between the neoadjuvant imatinib and upfront surgical patient groups in terms of gender (both had a male predominance) or age. All patients who were immunohistochemically tested were positive for CD34 (n=32) and DOG1 (n=28). Also, all genomically tested patients were positive for mutations in exon 11 of the KIT gene (n=14).

Reference

Tsukamoto S, Honma Y, Shoji H, et al. Clinical outcomes of surgical and imatinib treatment for rectal gastrointestinal stromal tumours: retrospective cohort study. BJS Open. 2022;6(3):zrac067. doi:10.1093/bjsopen/zrac067