Many Factors Cause Breast Cancer Drop
Less Hormone Therapy Usage Only 1 Reason, Study Shows
WebMD News Archive
May 3, 2007 - Breast cancer rates began dropping in the U.S. years before
women abandoned hormone therapy in large numbers, a new study shows.
This research shows factors other than a decline in hormone usage have
played a role in the downward trend.
Researchers from the American Cancer Society (ACS) analyzed invasive and
noninvasive breast tumor incidence rates from 1975 to 2003. They found that a
sharp drop in breast cancer cases between 2002 and 2003 was preceded by a less
dramatic drop among women 45 and older, beginning in 1999.
The most likely reason for the pre-2002 drop in cases, they say, was a
leveling off in the number of women in the U.S. getting mammograms.
“The decline in breast cancers since 2002 is due to a combination of
things,” ACS Strategic Director for Cancer Surveillance Ahmedin Jemal, DVM,
PhD, tells WebMD. “The decrease in hormone use has contributed, but so has the
stabilization in mammography usage.”
Rates Have Stabilized
Between 2002 and 2003, breast cancer rates reportedly dropped by nearly 7%
in the U.S., coinciding with a sharp drop in the use of hormone therapy
beginning in July of 2002.
That's when a large, federally funded trial of the estrogen and progestin
combination treatment Prempro was stopped early because of evidence of an
increased risk of breast cancer and heart disease in older women who took the
Last month, University of Texas M.D. Anderson Cancer Center researchers
Peter Ravdin, MD, PhD, and Donald Berry, MD, reported that breast cancer rates
began to stabilize at new lower rates beginning in mid-2003.
The finding bolstered their earlier research linking the decline in hormone
usage to the drop in breast cancers during that period.
Ravdin tells WebMD that the new ACS findings do not challenge this view.
“Clearly [the decline in breast cancers] is not being driven by just one
force,” he says. “This paper is a nice complement to ours.”
The ACS research team, lead by Jemal, examined breast cancer incidence rates
by tumor size, stage, and hormone receptor status among women aged 40 and older
from the mid-1970s through 2003.