Between 2002 and 2003, American women experienced a 7 percent decline in breast cancer incidence, which scientists attribute to the publicity surrounding results of the Women’s Health Initiative (WHI).

However, researchers led by Brian Sprague, Ph.D. have conducted a reevaluation of the post-WHI landscape that suggests otherwise.

“We found that the change in hormone therapy use only accounted for a decline of about 3 percent, so there’s another 4 percent that is being caused by something we do not yet know,” said Sprague, a postdoctoral fellow at the University of Wisconsin.

Results of this study were presented at the American Association for Cancer Research Frontiers in Cancer Prevention Research Conference, held Dec. 6-9 in Houston.

In 1991, the National Institutes of Health established the WHI to address the most common causes of death, disability and deterred quality of life among 15,730 postmenopausal women — cancer, cardiovascular disease and osteoporosis.

Results of the WHI demonstrated in 2002 that hormone therapy is linked with an increased risk of breast cancer. Other studies have confirmed this relationship, and many women have stopped taking hormone therapy due to concerns about the potential risk of cancer. At the same time, the incidence of breast cancer has declined, which researchers attribute to the decrease in hormone therapy use.

After conducting a thorough literature review of the decline in hormone use and the decline in breast cancer incidence, Sprague and colleagues estimated that 42 percent of the decline in incidence of breast cancer was linked to the cessation of hormone therapy use.

Sprague said that additional studies are needed to determine the source of the remaining decline in breast cancer cases.

“This does not mean that women should start taking hormones again, but there appear to be additional factors that have contributed to the decline in breast cancer,” he said.

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The mission of the American Association for Cancer Research is to prevent and cure cancer. Founded in 1907, the AACR is the world’s oldest and largest professional organization dedicated to advancing cancer research. The membership includes 30,000 basic, translational and clinical researchers; health care professionals; and cancer survivors and advocates in the United States and nearly 90 other countries. The AACR marshals the full spectrum of expertise from the cancer community to accelerate progress in the prevention, diagnosis and treatment of cancer through high-quality scientific and educational programs. It funds innovative, meritorious research grants, research fellowship and career development awards. The AACR Annual Meeting attracts more than 16,000 participants who share the latest discoveries and developments in the field. Special conferences throughout the year present novel data across a wide variety of topics in cancer research, treatment and patient care. The AACR publishes six major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; Cancer Epidemiology, Biomarkers & Prevention; and Cancer Prevention Research. The AACR also publishes CR, a magazine for cancer survivors and their families, patient advocates, physicians and scientists. CR provides a forum for sharing essential, evidence-based information and perspectives on progress in cancer research, survivorship and advocacy.

Source:  American Association for Cancer Research (AACR)