FRIDAY, Jan. 4 (HealthDay News) -- Chemotherapy or tamoxifen treatment may reduce the risk of contralateral breast cancer for five years or more after the initial diagnosis, according to study findings published in the Jan. 2 issue of the Journal of the National Cancer Institute.
Lisbeth Bertelsen, M.D., from the Danish Cancer Society in Copenhagen, Denmark, and colleagues reviewed a case group of 634 women with contralateral breast cancer and a control group of 1,158 women with unilateral breast cancer, all under 55 years of age. The researchers then evaluated the relationship between contralateral breast cancer and treatment with chemotherapy or tamoxifen.
The investigators found that the risk of contralateral breast cancer was lower after chemotherapy (rate ratio 0.57) or tamoxifen treatment (rate ratio 0.66). The lower risk after chemotherapy was significant for up to 10 years after diagnosis, and was stronger in women who became postmenopausal within one year of diagnosis (rate ratio 0.28). The lower risk after tamoxifen treatment continued and was significant for five years after diagnosis.
"The associations between chemotherapy and tamoxifen treatment and reduced risk for contralateral breast cancer appear to continue for 10 and five years, respectively, after the initial breast cancer is diagnosed," Bertelsen and colleagues conclude. "Ovarian suppression caused by chemotherapy may have a role in the association, possibly in combination with a cytotoxic effect on prevalent subclinical contralateral breast cancers."
Abstract
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