Complete GIST Resection Increased With Prolonged Preoperative Imatinib

Endoscopy image of small bowel GIST

The use of imatinib mesylate preoperatively for a maximum of 12 months resulted in a high rate of complete microscopic resection in a group of patients with marginally resectable gastrointestinal stromal tumor (GIST), according to the results of a phase II trial.

In addition, the neoadjuvant use of imatinib did not increase resistance to the drug, or result in high progression or complication rates, according to the results published in the International Journal of Surgical Oncology by Pierre Dub, MD, of the department of surgery, Maisonneuve-Rosemont Hospital, University of Montreal, Canada, and colleagues.

In recent years, researchers have begun to explore the use of imatinib, a drug proven to be effective in GIST, in adjuvant and neoadjuvant settings of the disease.

“Therapy with preoperative imatinib in marginally operable GIST is now recommended for consideration in both ESMO and NCCN guidelines,” Dub and colleagues wrote. “The major interest with preoperative imatinib in advanced GIST is its potential value as a method of tumor downsizing, where the goal is a less extensive surgery with less complications and a more complete resection.”

According to background information in the article, two prospective phase II studies recently reported promising results for the use of imatinib prior to surgery; however, patients were only exposed to the drug for 12 weeks.

In this study, Dub and colleagues enrolled 14 patients with advanced GIST and assigned them to receive imatinib daily for a maximum of 12 months. The purpose of the study was to see if prolonged use of imatinib resulted in a higher complete resection rate. Nine of the patients completed 12 months of preoperative imatinib.

After preoperative treatment, eight patients had stable disease and six had a partial response, according to RECIST criteria. Eleven of the patients underwent subsequent tumor resection and all of them achieved complete microscopic resection.

After a median 48 months of follow-up after surgery, the overall survival was 100% and the disease-free survival rate was 64%.

Treatment was relatively well tolerated with one patient reporting grade 3 nausea, three patients with adverse events related to tumor bleeding and one patient who required “semi-urgent surgical resection.”

In their discussion of the results, the researchers acknowledged that the study was done in a small group of patients; however, they added that it is the only trial that has looked at preoperative imatinib for such a prolonged period of time.

“With a median postoperative follow-up of 48 months, survival results are mature,” they wrote. “In marginally respectable GIST, we recommend at least 6 months of preoperative imatinib to all patients.”