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A cancer treatment that can cause cancer?

Jan 07, 2015 02:00PM ● By Cate Reynolds
The risk of developing leukemia after radiation therapy or chemotherapy for early stage breast cancer remains very small, but it is twice as high as previously reported, according to results of a new study led by researchers at the Johns Hopkins Kimmel Cancer Center.

The study team reviewed data on 20,063 breast cancer patients treated at eight U.S. cancer centers between 1998 and 2007 whose cancer recurrence and secondary cancer rates were recorded in a database kept by the National Comprehensive Cancer Network. In that group, 50 patients had developed some form of leukemia within 10 years after radiation therapy, chemotherapy or a combination of the two. That translates to roughly a cumulative risk of 0.5 percent.

“The frequency of bone marrow cancers such as leukemia is small, there’s no question about it,” Karp says. “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.” Results of their so-called look-back, or retrospective, study were published online Dec. 22 in the Journal of Clinical Oncology.

“Most medical oncologists have come to think that the risk is early and short-lived,” says Karp. “So this was a little bit of a wake-up call that we are not seeing any plateau of that risk, and it is higher.” Antonio Wolff, M.D., a professor of oncology at the Johns Hopkins University School of Medicine, says the study could help early-stage breast cancer patients and their physicians think more carefully about the use of chemotherapy for “just-in-case” reasons, especially when patients have a low risk of cancer recurrence.

“Our study provides useful information for physicians and patients to consider a potential downside of preventive or adjuvant chemotherapy in patients with very low risk of breast cancer recurrence,” says Wolff. “It could be a false and dangerous security blanket to some patients by exposing them to a small risk of serious late effects with little or no real benefit from the treatment.”

In recent years, oncologists have learned that postsurgical chemotherapy for breast cancer mostly benefits a small and select group of patients. The National Comprehensive Cancer Network clinical guidelines no longer recommend it for all patients with stage 1 breast cancers, the term for invasive breast cancers no larger than 2 centimeters that have not spread to nearby lymph nodes.

--Sarah Hagerty
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