Research by Memorial Sloan-Kettering Cancer Center investigators suggests that patients taking imatinib (GleevecŪ) to treat chronic myeloid leukemia (CML) or gastrointestinal stromal tumors (GIST) may experience changes in bone metabolism. The results, published May 11 in the New England Journal of Medicine, indicate that imatinib, in addition to inhibiting proteins responsible for CML and GIST, blocks a receptor important to bone synthesis and remodeling. This is the first time such a side effect has been noted.

The effect was observed when researchers reviewed pharmacy records of 77 Memorial Sloan-Kettering patients who had received imatinib in 2002 and 2003, 49 of whom had had at least one measurement taken for blood phosphate -- a mineral essential for bone metabolism. Of the 49 patients, 25 had low phosphate levels, and 16 of these (8 with CML, 8 with GIST) underwent additional biochemical evaluation, revealing abnormal bone metabolism.

"If our findings are confirmed," said Memorial Sloan-Kettering medical oncologist Ellin Berman, the paper's first author, "patients receiving this type of drug might need to be monitored for serum phosphate levels during imatinib therapy so that phosphate replacement can be started. We are now trying to determine whether these metabolic abnormalities directly affect bone structure."

To learn more about how Gleevec may alter bone metabolism, please visit the website for the Memorial Sloan-Kettering Cancer Center (http://www.mskcc.org/mskcc/html/70158.cfm).