WEDNESDAY, May 10 (HealthDay News) -- In patients with chronic myelogenous leukemia or gastrointestinal stromal tumors, including those with normal serum phosphate levels, imatinib mesylate (Gleevec) therapy may cause changes in bone and mineral metabolism and inhibit bone remodeling, according to a study in the May 11 issue of the New England Journal of Medicine.
Ellin Berman, M.D., of Memorial Sloan-Kettering Cancer Center in New York City, and colleagues studied 24 cancer patients on imatinib, including 16 with low serum phosphate levels and eight with normal levels.
Compared to patients in the normal-phosphate group, those in the low-phosphate group had elevated parathyroid hormone levels and low-to-normal serum calcium levels, were younger and were getting a higher dose of imatinib. In addition, both groups had high levels of phosphate in excreted urine and strikingly decreased serum levels of osteocalcin and N-telopeptide of collagen cross-links.
"Although imatinib inhibits tyrosine kinases associated with specific diseases, our data suggest that in vivo inhibition of the platelet-derived growth factor receptor may also occur and may have clinical consequences," the authors conclude. "If this is confirmed, routine monitoring of serum phosphate and vitamin D during imatinib therapy may be advisable so that prompt phosphate replacement can be initiated."
One of the authors later became an employee of Novartis, while another has received lecture fees from the company.
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