(HealthDay News) — Among early-stage breast cancer patients who undergo chemotherapy and/or radiation treatment, the risk for developing treatment-related leukemia, though low, is still double what experts had previously thought, a new analysis reveals.

Reporting online in the Journal of Clinical Oncology, the researchers said the findings should give pause to doctors and breast cancer patients who are considering post-surgical treatment options.

The finding comes from a review of 20,063 breast cancer cases treated between 1998 and 2007.

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“The frequency of bone marrow cancers such as leukemia is small, there’s no question about it,” study lead author Judith Karp, MD, professor emerita of oncology at the Johns Hopkins University School of Medicine in Baltimore, noted in a university news release.

“However, the cumulative risk over a decade is now shown to be twice as high as we thought it was, and that risk doesn’t seem to slow down five years after treatment,” she said.

Patients included in the review had been treated at eight different cancer centers across the United States, and information on their post-treatment health came from the National Comprehensive Cancer Network (NCCN). The records showed that 50 patients developed leukemia within a decade following exposure to breast cancer chemotherapy, radiation, or both. That translates into 0.50% of all treated patients — a figure that is twice the rate of 0.25% of patients seen in prior studies.According to Karp’s team, those earlier studies were based on much smaller groups of patients — usually just a few hundred people.

At issue is whether or not patients with a very low risk for breast cancer recurrence always need “just-in-case” chemotherapy or radiation, given that the risk for leukemia may be greater than previously assumed. For example, stage 1 breast cancer patients with very small localized tumors that have not spread to the lymph nodes may not want to incur any degree of added leukemia risk, when the potential benefit of post-surgery treatment might be negligible.

In addition, the NCCN no longer recommends that postoperative chemotherapy be standard for all stage 1 patients, Karp’s team noted in the news release.

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