Data published today online and in an upcoming print issue of The Lancet show that imatinib mesylate tablets (GleevecR) when taken after surgery, substantially reduces the rate of recurrence of Kit-positive gastrointestinal stromal tumors (GIST) compared with placebo.

The Phase III study was led by the American College of Surgeons Oncology Group (ACOSOG) and examined post-surgery, or adjuvant, treatment of more than 700 GIST patients. Researchers found that 98% of patients receiving 400 mg of Gleevec daily remained tumor-free one year after surgery. The study also found Gleevec to be safe and well-tolerated, with a low rate of serious adverse events.

Historically, one in two patients experienced recurrence of GIST within a median of two years after surgery

"The standard of care after surgical removal of primary GIST has been clinical and radiologic observation, since standard chemotherapeutic agents have been ineffective in this disease. This frequently resulted in tumor recurrence," said Ronald DeMatteo, MD, Memorial Sloan Kettering Cancer Center, New York, NY. "Now, as The Lancet reports, by treating patients with Gleevec after removal of their initial tumor, we can proactively impact the course of this disease by delaying, and in some patients possibly preventing, the return of the cancer."

The double-blind, randomized, multicenter study was conducted throughout the US and Canada. It included 713 GIST patients whose tumors had been surgically removed. The study compared the recurrence-free survival (RFS) of patients taking either Gleevec 400 mg daily or placebo immediately following surgery. The results showed that 98% of those receiving Gleevec remained recurrence-free one year following surgery compared with approximately 83% of those receiving placebo (P<0.0001).

The investigators reported that Gleevec therapy was well tolerated by most patients, with side effects similar to those observed in previous clinical trials with Gleevec. These include nausea, diarrhea and swelling (edema).

Gleevec was recently approved in the US, Switzerland and several other countries for the treatment of Kit-positive GIST in the adjuvant setting, based on the ACOSOG data. Further follow up is necessary to understand the continued impact on prevention of recurrent disease and overall survival.