[PHNUTR-L] Decrease in breast cancer incidence linked to drop in hormone replacement

[Kathrynne Holden]

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Public release date: 18-Apr-2007
http://www.eurekalert.org/pub_releases/2007-04/labr-dib041307.php

Contact: Rowan Chlebowski
rchlebow at whi.org
310-748-7463
Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center 
(LA BioMed)

Decrease in breast cancer incidence linked to drop in hormone replacement

20 million fewer prescriptions responsible for sharp decline

TORRANCE, Calif. (April 19, 2007) - A special report in the April 19, 
2007 edition of The New England Journal of Medicine concludes that the 
sharp decline in breast-cancer incidence in 2003, followed by a relative 
stabilization at a lower rater in 2004, is most likely related to the 
first report of the Women's Health Initiative (WHI) (JAMA 2002; 
288:321-333. Risks and benefits of estrogen plus progestin in healthy 
postmenopausal women…) and the ensuing drop in hormone-replacement 
therapy among postmenopausal women.

The report shows that the age adjusted incidence rate of breast cancer 
in women in the United States fell sharply by 6.7% in 2003, as compared 
with the rate in 2002. Data from 2004 showed a leveling-off relative to 
the 2003 rate with little additional decrease. The decrease was evident 
only in women who were 50 years of age or older and was more evident in 
cancers that were estrogen-receptor (ER)-positive than in those that 
were ER-negative.

The reports' lead author is Peter Ravdin, M.D., of the Anderson Cancer 
Center, and included investigators from the National Cancer Institute 
and the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical 
Center (LA BioMed). Rowan Chlebowski, MD, PhD, a principal 
investigator/oncologist at LA BioMed, and the only researcher to 
participate in the 2002 reports of the trial evaluating estrogen plus 
progestin (which led to the decrease in menopausal hormone therapy use 
in 2003) and the 2006-07 studies outlining the subsequent decrease in 
breast cancer, states: "While the cause of the reduction is not 
definitive, the sustained decrease in new breast cancer diagnosed in the 
U.S. is a remarkable event. We estimate 44,000 fewer breast cancers over 
those two years (2003-04) and thousands more in the coming decades."

Researchers looked at several variables that could be responsible for 
such a decline. They looked for flaws in the data itself, changes in 
reproductive factors, changes in mammographic screening, changes in 
environmental exposures, changes in diet, and changes in use of 
hormone-replacement therapy. Only the use of hormone-replacement therapy 
changed substantially, with the total number of prescriptions for the 
two most commonly prescribed forms of hormone-replacement therapy in the 
United States - Premarin and Prempro - having their steepest declines 
starting in 2002 and particularly in 2003 (62 million scripts in 2000, 
61 million in 2001, 47 million in 2002, 24 million in 2003, 21 million 
in 2004, and 18 million in 2005).

The reduction of hormone-replacement therapy could have caused a 
decreased incidence of breast cancer by direct hormonal effects on the 
growth of occult breast cancers, a change that would have affected 
predominantly ER-positive tumors. The rapidity of the change suggests 
that clinically occult breast cancers stopped progressing or even 
regressed soon after the discontinuation of the therapy. The hypotheses 
is that hormone withdrawal can rapidly influence the growth of breast 
cancer is supported by anecdotal reports of regression of breast cancer 
after discontinuation of hormone replacement therapy.
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
"Ask the Parkinson Dietitian"  http://www.parkinson.org/
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