Latest Data From Kaiser Permanente and California Cancer Registry Shows
Drop
OAKLAND, Calif., Dec. 6 /PRNewswire/ -- Research scientists at the
Northern California Cancer Center and Kaiser Permanente's Division of
Research have found significant reductions in both the use of hormone
replacement therapies and the incidence of breast cancer in California in
the years following the release of the 2002 Women's Health Initiative (WHI)
trial results. The data appear in the November 20 issue of the Journal of
Clinical Oncology.
Previous studies have shown that long-term use of hormone therapy is
linked to increased risk of breast cancer. For example, the WHI randomized
trial and other studies discovered that estrogen plus progestin hormone
therapy use increased a woman's risk of breast cancer.
This new analysis, the first to use the most recent 2004 California
Cancer Registry data, supports the theory that women who discontinue
hormone therapy use may reduce their chances of being diagnosed with breast
cancer.
"Hormone therapy use dropped 68 percent between 2001 and 2003, and
shortly thereafter we saw breast cancer rates drop by 10 to 11 percent.
This drop was sustained in 2004, which tells us that the decline wasn't
just a fluke," notes Dr. Christina A. Clarke, the Northern California
Cancer Center scientist who led the study.
In the current study, researchers examined yearly prevalence of hormone
therapy use and breast cancer incidence from 1994 to 2003 for women ages 50
to 74 in Kaiser Permanente's Northern California Region and in the 2004
California Cancer Registry. They found consistent evidence of corresponding
trends in decline in both hormone therapy use and breast cancer incidence.
"We can't say that changes in hormone therapy use caused the decline in
breast cancer, because these data don't link hormone users directly to
breast cancer diagnoses, but they are certainly suggestive," adds Dr. Lisa
Herrinton from Kaiser Permanente's Division of Research. "If it holds up
over time, a 10 percent decline in breast cancer incidence is really
striking. It amounts to an annual reduction of about 10,000 breast cancer
cases in women aged 50 to 74."
Similar studies on the decline of breast cancer incidence in the United
States will be presented by different researchers at the San Antonio Breast
Cancer Symposium next week, though only data from 2003 is presented. The
Northern California Cancer Center/Kaiser Permanente study includes data
through 2004, and it provides information on hormone therapy for the same
population.
From their analysis, researchers maintain that breast cancer incidence
trends need to be monitored closely in regard to patterns of hormone
therapy use. "Based upon what we know about the biology of hormone therapy,
the declines make a lot of sense, and we want to continue to track these
parallel trends," says Clarke.
The Northern California Cancer Center (http://www.nccc.org) is an established,
nationally recognized leader dedicated to understanding the causes and
prevention of cancer and to improve the quality of life for individuals
living with cancer. NCCC has been working with scientists, educators,
patients, clinicians, and community leaders successfully since 1974, and is
an active partner with Stanford University's Comprehensive Cancer Center.
NCCC is a 501(c)3 nonprofit with over 160 employees and a $15 million
operating budget.
The Kaiser Permanente Division of Research conducts, publishes, and
disseminates epidemiologic and health services research to improve the
health and medical care of Kaiser Permanente members and the society at
large. It seeks to understand the determinants of illness and well-being
and to improve the quality and cost-effectiveness of health care.
Currently, DOR's 400-plus staff is working on more than 250 epidemiological
and health services research projects.
SOURCE Kaiser Permanente
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