Patients with a favorable lab result had an 84 percent chance of a partial remission in response to Gleevec, while none of the patients with an unfavorable lab result had a partial remission.
"These results demonstrate that the most important predictor of tumor shrinkage during Gleevec therapy is not patient age, overall health status, or tumor size, but rather the specific type of mutation causing the tumor," said Michael Heinrich, M.D., member of the Oregon Health & Science University Cancer Institute, associate professor of medicine (hematology and medical oncology) in the OHSU School of Medicine and the Portland VA Medical Center, and co-principal investigator of the study.
Gastrointestinal stromal tumors (GISTs), which occur in the stomach and intestines, are diagnosed in up to 10,000 Americans annually. Surgery is the treatment of choice for localized tumors, but in many patients the tumor recurs and spreads elsewhere, particularly to the liver. Up until two years ago, at this metastatic stage, the disease was invariably fatal because chemotherapy, radiation and surgery are ineffective in advanced cases. More recently, however, physicians have shown that metastatic GISTs are responsive to Gleevec.
Gleevec, technically known as a tyrosine kinase inhibitor, was first introduced for the treatment of chronic myelogenous leukemia (CML), the growth of which is driven by a mutant tyrosine kinase enzyme called BCR-ABL. Gleevec is a potent inhibitor of the BCR-ABL enzyme, effectively shutting down the growth of leukemia cells with relatively minor side effects.