NEW YORK (Reuters Health) - Older women with breast cancer who undergo chemotherapy have a small but significant increased risk of developing acute myeloid leukemia (AML), new research shows.

The findings stem from an analysis of data for women diagnosed with breast cancer from 1992 to 2002 and entered in a Medicare-linked database.

The study focused on the treatments received by women with or without a diagnosis of AML, senior author Dr. Sharon H. Giordano and colleagues, from the University of Texas, M. D. Anderson Cancer Center in Houston, note in the Journal of Clinical Oncology.

Of the 64,715 women included in the study, 10,130 had received chemotherapy in addition to other surgery and 54,585 had not. Patients ranged in age from 66 to 104 years and the average follow-up period was 54.8 months.

Women treated with chemotherapy had a 1.8 percent chance of developing AML at 10 years. The risk in other patients was significantly lower -- 1.2 percent. After accounting for other factors, the difference translated into a relative increase in risk of 53 percent for AML associated with chemotherapy.

"Decisions regarding adjuvant chemotherapy in older women must incorporate both short- and long-term risks of chemotherapy as well as potential benefits, so that patients can make informed decisions," Giordano and colleagues conclude.

SOURCE: Journal of Clinical Oncology, September 1, 2007.