Preliminary results from a large randomized clinical trial show that imatinib given after complete resection of primary gastrointestinal stromal tumor decreases risk of recurrence compared with surgery alone, according to researchers from the American College of Surgeons Oncology Group (ACOSOG).

The data monitoring committee overseeing the ACOSOG Z9001 Trial has recommended that the results from a recent interim analysis be made public because the study had met its primary endpoint of increasing recurrence-free survival.

Information on over 600 patients enrolled in the study was used in the analysis. Patients participated through one of five North American Cooperative Oncology Groups, led by ACOSOG and including Cancer and Leukemia Group B, Eastern Cooperative Oncology Group, Southwest Oncology Group, and the National Cancer Institute of Canada, Clinical Trials Group.

Patients with primary tumors three centimeters or larger that had been completely removed with surgery were enrolled in the trial between June 2002 and April 2007. Patients were randomized to one of two treatment arms. One patient group received imatinib 400 milligrams per day for one year. The second group received placebo for one year.

Patients who developed recurrence while on study therapy were unblinded to treatment assignment. Patients who had been on placebo subsequently received imatinib and those who had been on imatinib continued imatinib therapy, but at a higher dose. There was no difference in overall survival for patients in the two treatment arms.

"The standard treatment for primary gastrointestinal stromal tumor is complete surgical removal of the tumor without additional therapy," said Elias A. Zerhouni, MD, Director of the National Institutes of Health. "It is excellent news that addition of this well-tolerated cancer pill to the treatment regimen can have such a positive impact on decreasing the risk of recurrence."

Researchers found that approximately 97 per cent of patients who received one year of imatinib after surgery did not have a recurrence compared with 83 percent of patients who received one year of placebo.

In addition, imatinib therapy was well tolerated by most patients enrolled in the study. The types of side effects observed in the trial were similar to those observed in other clinical trials with imatinib and included nausea, diarrhea, and edema. Presentation of detailed results from this trial is planned for a future scientific meeting.

"These results have major implications for patients with primary gastrointestinal stromal tumor (GIST)," noted principal investigator Ronald DeMatteo, MD, Memorial Sloan-Kettering Cancer Center, New York, N.Y. "Conventional chemotherapy agents have been notoriously ineffective in GIST. This study for the first time demonstrated that targeted molecular therapy reduces the rate of recurrence after complete removal of a primary GIST."