Hormonal Therapy Link to Breast Cancer Explored

Combination hormone therapy, not mammography frequency, associated with increased breast cancer incidence

WEDNESDAY, Feb. 4 (HealthDay News) -- A decline in the use of combined hormone therapy appears responsible for a decreased incidence of breast cancer among women, according to research published Feb. 5 in the New England Journal of Medicine.

Rowan T. Chlebowski, M.D., Ph.D., of the Harbor-UCLA Medical Center in Torrance, Calif., and colleagues evaluated the results of the Women's Health Initiative study, which randomized women to receive either a combination of conjugated equine estrogens plus medroxyprogesterone or placebo. The investigators also assessed other risk factors for breast cancer to determine their impact on breast cancer incidence.

During the first two years of the study, fewer breast cancer diagnoses were observed among women receiving combination hormonal therapy. However, over the subsequent study years, women in the combination hormonal therapy group experienced nearly twice the incidence of breast cancer diagnoses and this increased until the women stopped taking their pills, after which this elevated risk decreased rapidly, the researchers report. Although this decline coincided with a decreased use of hormonal therapy, there was no difference in the frequency of mammography, the report indicates.

"This finding supports the hypothesis that the recent reduction in the incidence of breast cancer among women in certain age groups in the United States is predominantly related to a decrease in the use of combined estrogen plus progestin," the authors write.

Several of the study authors report financial relationships with the pharmaceutical industry.

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