Patients operated on for gastrointestinal stromal tumors (GISTs) live longer without their disease coming back if they receive the drug imatinib (Gleevec®) as an adjuvant (additional) therapy after surgery. This is the conclusion of the first nationwide study ever performed in GIST patients. The study by Ronald DeMatteo, who heads Memorial Sloan Kettering’s Division of General Surgical Oncology, and colleagues was published in the March 18 issue of The Lancet. [PubMed Abstract]
Conventional chemotherapy is almost never effective against GIST, a rare cancer of the digestive tract. Patients diagnosed with a local tumor are usually treated with surgery alone, but many develop tumor recurrence later in life. For about a decade, the targeted therapy imatinib has been used successfully in patients with metastatic GIST.
“Our study shows that imatinib also can be given preventively to help patients who are operated on for GIST to stay tumor-free,” said Dr. DeMatteo. He and his colleagues followed 713 such patients, who received either imatinib or placebo after their surgery. After one year, only 2 percent of patients receiving the drug had tumor recurrence, compared with 17 percent of those on placebo. Based on these results, the Food and Drug Administration recently approved the use of imatinib as adjuvant therapy after surgery in GIST patients.
Like other targeted therapies, imatinib was designed to thwart a molecular mechanism that causes disease. A majority of GIST patients respond to the drug as their tumors have mutations in either of two genes, KIT or PDGFR. “Imatinib is the first drug of its kind shown to prevent metastases from forming after a primary tumor has been removed,” Dr. DeMatteo remarked. “We hope to see similar treatment strategies emerge for other diseases, such as lung and kidney cancer, for which Memorial Sloan Kettering is at the frontline of exploring targeted therapies.”
Adjuvant imatinib had a particularly dramatic effect in patients with large tumors. The investigators are now examining whether factors other than tumor size, such as a tumor’s location or molecular profile, can help physicians in determining which patients should receive the drug after surgery.