According to an article published in the Journal of Clinical Oncology, interruption in treatment with Gleevec® (imatinib mesylate) is not recommended for patients with gastrointestinal stromal tumors (GIST) whose disease has appeared to stabilize.
GIST is a rare type of cancer that originates in the wall of the gastrointestinal track. The American Cancer Society estimates that only approximately 5,000 individuals are diagnosed annually with GIST in the U.S. GIST is thought to originate in the “pacemaker” cells of the digestive system; these cells are responsible for the movement of food or nutrients through the system.
Standard treatment for GIST typically includes surgical removal of as much cancer as possible and treatment with the targeted agent Gleevec. Because GIST remains virtually unresponsive to standard chemotherapy or radiation therapy, effective treatment options are limited.
Gleevec is a biological agent that is approved for the treatment of GIST as well as chronic myeloid leukemia (CML). Gleevec has activity in several biological pathways implicated in the development and/or expression of cancer. It tends to bind to targets within a cell and slows or stops the uncontrolled growth of the cancer cells with certain genetic mutations. Because the disease is often stabilized while a patient is being treated with Gleevec, researchers have questioned whether disease stabilization would be maintained if these patients were taken off Gleevec for a period.
To address the question of whether treatment with Gleevec may be intermittently stopped among patients with GIST whose cancer had been stabilized, researchers from France recently conducted a clinical trial to compare outcomes of patients who continuously receive treatment with Gleevec with those who stop treatment with Gleevec. This trial included 58 patients whose cancer had been stabilized for at least one year under treatment with Gleevec. One group of patients was treated with continuous (CONT) Gleevec, and another group was treated with interrupted (INT) Gleevec.
- At last follow-up, of the 26 patients in the CONT group, only eight had experienced cancer progression, while 26 of the 32 patients in the INT group had experienced cancer progression.
- There were no differences in overall survival or quality of life between the two treatment groups.
- Twenty four of the 26 patients in the INT group who experienced cancer progression responded to subsequent treatment with Gleevec.
The researchers concluded that interruption in therapy with Gleevec for patients with GIST whose disease is stabilized for at least one year on treatment with Gleevec cannot be recommended unless patients experience severe side effects from therapy. The authors state specifically that “Imatinib interruption results in rapid progression in most patients with advanced GIST, and cannot be recommended in routine practice unless patient experience significant toxicity.”
Reference: Blay J-Y, Le Cesne A, Ray-Coquard I, et al. Prospective multicentric randomized Phase III study of imatinib in patients with advanced gastrointestinal stromal tumors comparing interruption versus continuation of treatment beyond 1 Year: The French Sarcoma Group. Journal of Clinical Oncology. 2007; 25: 1107-1113.