Chemotherapy drugs could lead to bone loss.

A study indicates that medication to reduce the toxic effects of chemotherapy could induce bone loss and help tumors grow in bone. The findings prompted researchers to recommend increased awareness of bone health during cancer treatments.

Since chemotherapy can destroy white blood cells that are important in fighting infection, cancer patients often receive a growth factor called granulocyte colony-stimulating factor, or G-CSF, to help them recover healthy blood counts after treatment. Use of GCSF recently has increased because by speeding blood cell regrowth, it allows patients to undergo more intensive chemotherapy regimens in which anticancer agents are given at more frequent intervals.

In the study, researchers examined the impact of G-CSF on bone development in mice. The results showed that an eight-day course of G-CSF alone without chemotherapy significantly decreased bone mineral density. Mice that received G-CSF also demonstrated significantly increased tumor growth in bone.

G-CSF increased the number and activity of bone cells called osteoclasts, which destroy and remove bone material as part of the normal process of bone turnover. The resulting loss of bone density created a favorable environment for bone tumor growth.

When the researchers injected melanoma or breast cancer cells into mice, the mice getting G-CSF developed a two-fold increase in tumor burden, a measure of the size and severity of tumors, compared with those that did not receive G-CSF.

Although G-CSF had a strong effect on bone metastasis in the experimental mice, early clinical trials in humans using G-CSF with chemotherapy have so far shown no adverse effects on survival and no increase in bone metastasis. In fact, breast cancer patients undergoing dose-dense chemotherapy with G-CSF support tend to have a longer disease-free period than those getting standard dosing without G-CSF. The study appeared in the Dec. 27, 2006, online issue of Blood.