Drug is shown to be most effective on larger tumors
Taking Gleevec after surgery to remove a gastrointestinal stromal tumor improves tumor-free survival, a U.S. study has confirmed.
Gastrointestinal stromal tumors (GIST), the most common soft-tissue cancer of the intestinal tract, typically occur in the stomach or small intestine. About 3,000 to 4,000 cases are diagnosed in the United States each year. According to background information in the study, about 85 percent of these tumors have a protein that allows them to be inhibited by Gleevec, known as imatinib.
The finding stems from a phase 3 trial for the drug, which was approved last year by the U.S. Food and Drug Administration to treat people who’ve had surgery to remove a GIST. The drug already was approved for treating certain types of adult leukemia.
The trial included more than 700 people with a GIST at least 3 centimeters in size that tested positive for the protein. The participants were randomly selected to take either 400 milligrams of Gleevec or a placebo once a day for a year after surgery to remove their tumor.
After a median follow-up of almost 20 months, 8 percent of people in the Gleevec group and 20 percent of those in the placebo group had experienced tumor recurrence or had died. After a year, recurrence-free survival was 98 percent for those taking the drug and 83 percent for people taking the placebo.
Tumor size affected treatment success, the study found. Gleevec had the most effect on tumors that were 10 cm or larger, less effect on tumors between 6 and 10 cm, and the least effect on tumors between 3 and 6 cm, the study reported.
The most common serious side effects experienced by people taking the drug were dermatitis, abdominal pain and diarrhea.
Dr. Ronald DeMatteo, of Memorial Sloan-Kettering Cancer Center, and his fellow researchers said that their “findings will affect the management of patients with primary gastrointestinal stromal tumor and could have relevance to the adjuvant use of other molecular agents for cancer.”
The study appears online and in an upcoming print issue of The Lancet.
Dr. Peter Hohenberger, of the University of Heidelberg, in Mannheim, Germany, said in an accompanying comment that more research is needed.
“There are so many unknowns that this trial might not be able to provide a definitive treatment decision,” he wrote. “To refine the indication for adjuvant treatment remains the big task for future studies.”