THURSDAY, Aug. 9 (HealthDay News) -- A drop in hormone therapy use in California was mirrored by a drop in breast cancer rates, with counties with the biggest decline in hormone replacement therapy (HRT) having a greater decline in cancer, according to the results of a large population-based study published in the Aug. 10 issue of the Journal of Clinical Oncology. At the same time, mammography rates remained stable, suggesting that the cancer decline may indeed have been due to a drop in HRT use.
Anthony Robbins, M.D., Ph.D., of the California Cancer Registry in Sacramento, Calif., and a colleague analyzed data from the registry that included nearly 3 million non-Hispanic white women aged 45 to 74. The researchers divided counties into three groups based on estrogen-progestin hormone therapy (EPHT) use in 2001. They then analyzed trends in the age-adjusted incidence of breast cancer in these counties compared to changes in hormone use.
Large regional differences were detected in the incidence of breast cancer and EPHT use between 2001-2004. Breast cancer incidence declined by 8.8 percent in counties with the smallest change in EPHT, by 13.9 percent in counties with an intermediate reduction, and by 22.6 percent in counties with the largest drop in EPHT.
"These data support the hypothesis that changes in EPHT use in 2002 may be responsible for significant declines in breast cancer incidence between 2002 and 2003 and sustained through 2004," conclude the authors. "The role of EPHT in breast carcinogenesis may be as a promoter, fueling the growth of small, subclinical tumors, particularly those that are hormone sensitive."
Abstract
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