Women with breast cancer who receive granulocyte- or granulocyte-macrophage colony stimulating factor while receiving chemotherapy may be at increased risk for acute myelocytic leukemia and myelodysplastic syndrome, according to an article in the February 7 issue of Journal of the National Cancer Institute.

The authors note that the absolute risk is very small, but that risk should still be taken into consideration when making treatment decisions.

However, there is some concern that growth factors may keep cells alive that have been mutated by chemotherapy into malignant phenotype. Indeed, some studies have hinted that cancer patients who receive growth factors with chemotherapy may have an increased risk of these two diseases.

Dawn Hershman, MD, of the Herbert Irving Comprehensive Cancer Center at Columbia University Medical Center and New York Presbyterian Hospital, and colleagues set out to determine the association between colony stimulating factor use and the risk of either leukemia or myelodysplastic syndrome among women treated with chemotherapy for early-stage breast cancer.

The US researchers identified 5,510 American women age 65 years and older who were diagnosed with breast cancer and treated with chemotherapy between 1991 and 1999. A total of 906 (16 percent) were treated with at least one course of G-CSF (832), GM-CSF (29), or both (49).

Among the 906 patients who received one or both growth factors, 16 (1.77 percent) developed either the leukemia or syndrome; among the 4,604 women who did not get growth factor treatment, 48 (1.04 percent) developed one of the diseases. Women who received either colony stimulating factor had twice the risk of developing one of the hematological conditions as women not treated with the growth factors.

“Our study demonstrates that the elevated risk of AML or MDS associated with adjuvant chemotherapy may be further increased by the concurrent use of growth factors,” the authors wrote. “It is unclear if the growth factors cause an increased risk or if the requirements for their use cause an increased risk; however, the absolute overall risk appeared to be small, even among the elderly patients we studied. Nevertheless, if further research confirms this finding, this risk should be factored into clinical decisions with regard to the use of growth factors.”