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Science Forum Index » Medicine - Cancer Forum » U.S. breast cancer rates down by 7 per cent
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| Roman Bystrianyk |
 Posted: Thu Dec 14, 2006 10:04 pm |
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"U.S. breast cancer rates down by 7 per cent", Globe and Mail, December
14, 2006,
Link:
http://www.theglobeandmail.com/servlet/story/RTGAM.20061214.wbcancer1214/BNStory/specialScienceandHealth/home
U.S. breast cancer rates plunged an unprecedented 7 per cent in 2003,
the year after millions of women stopped taking menopause hormones when
a study showed the pills raise the risk of tumours.
The startling new analysis, reported Thursday at the San Antonio Breast
Cancer Symposium, does not prove a link between hormone therapy and
breast cancer, but strongly suggests it, many experts said.
"When I saw it, I couldn't believe it," statistician Donald Berry
of the University of Texas M.D. Anderson Cancer Center in Houston said
of the drop.
Cancers take years to form, so going off hormones would not instantly
prevent new tumours. But tumours that had been developing might stop
growing, shrink or disappear so they were no longer detected by
mammograms, doctors theorized.
Cases dropped most among women 50 and older - the age group taking
hormones. The decline was biggest for tumours whose growth is fuelled
by estrogen - the type most affected by hormone use.
The drop was seen in every single cancer registry that reports
information to the federal government, and no big change occurred with
any other major type of cancer. These are strong signs that the breast
cancer decline is no statistical fluke or error.
"It's a big deal ... amazing, really," said another of the
researchers, Dr. Rowan Chlebowski of Harbor-UCLA Medical Center in Los
Angeles. "It's better than a cure" because these are cases that
never occurred, he said.
About 200,000 cases of breast cancer had been expected that year; the
drop means that about 14,000 fewer women actually were diagnosed with
the disease.
A separate study by the American Cancer Society, currently in press
with a medical journal, also documents the drop. Lead author Ahmedin
Jemal attributes two-thirds of it to a decline in hormone use and the
rest to mammography use levelling off, resulting in fewer tumours being
detected.
"We are really trying to look at the big picture," he said. "You
cannot rule out the effect of screening."
Breast cancer is the most common major cancer in American women and the
second leading cause of cancer deaths in women. About 213,000 new cases
are expected to occur in the United States this year and more than 1
million worldwide.
Incidence in the United States rose almost 2 per cent per year from
1990 to 1998, then began to slightly decrease, said Dr. Peter Ravdin,
the M.D. Anderson doctor who led the new analysis and presented results
at the Texas cancer meeting.
In July 2002, the federal Women's Health Initiative study was stopped
after more breast cancers and heart problems occurred among women
taking estrogen-progestin pills.
That led to new warning labels on the drugs and doctor groups urging
women to use the lowest dose for the shortest time possible for hot
flashes and other menopause symptoms.
Within a year, about half of women who had been taking hormones
stopped. Prescriptions had been steady at around 22 million each
quarter, but plummeted to 12.7 million in the last quarter of 2003,
according to IMS Health, which tracks drug sales.
Breast cancer rates declined, too. In 2002, there were roughly 134
cases per 100,000 women - a 2.5 per cent drop from about 137 the
previous year. In 2003, there were only 124 cases per 100,000 women -
about a 7 per cent drop over 2002. That is the most significant decline
in the breast cancer rate since records have been kept beginning in the
1970s.
(Rates are used rather than raw numbers because they give a better
picture of the situation as the population shifts and ages.)
Researchers saw an even stronger trend when they looked month-to-month.
Cases dropped 6 per cent in the first half of 2003 and 9 per cent in
the second half.
Estrogen-sensitive tumours declined twice as much as tumours that are
not fuelled by estrogen. The decline in incidence among women ages
50-69 was three times that of other age groups.
The numbers come from the National Cancer Institute's surveillance
database, which uses cancer registries around the country to project
national incidence and death rates.
When the 2003 numbers were first released a few months ago, they were
grouped with 2001 and 2002 and portrayed as a levelling off of breast
cancer after decades of steady rise. The big single-year drop was not
pointed out.
"You don't want to over interpret one point" without knowing
whether it is a trend, said Kathy Cronin, a National Cancer Institute
statistician who worked on the new analysis.
"The major health organizations have been cautious because of not
wanting to call attention to something of this much interest to
everyone prematurely," said Dr. Michael Thun of the cancer society.
Dr. Ravdin disagreed.
"It doesn't have to be a trend to be real," he said. "Such a
rapid effect is most consistent with the idea that cancers that were
already there ... were actually being stopped in their growth to the
point where they would not be detected."
It is not known whether these tumours will regress and never become a
problem or just take longer to show up, he said.
However, doctors already know that withdrawing hormones causes tumours
to shrink. If a woman with estrogen-sensitive breast cancer has her
ovaries removed, "her tumour will stop growing immediately," Dr.
Ravdin said.
Dr. JoAnn Manson, a women's health expert at Harvard-affiliated Brigham
and Women's Hospital in Boston who has a new book out on hormones and
menopause, thinks the big drop in breast cancer cases could be due to
hormones, "especially a reduction in long duration of use."
"It's also possible that a trend toward lower doses of hormones has
played a role," she said.
She and other doctors are continuing to study women in the big federal
study who had been on hormones and then quit.
Federal statistics for 2004 are expected in April. Information from one
large registry, California's, published recently in the Journal of
Clinical Oncology, hints that the trend is continuing. |
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| Tim Jackson |
| Posted: Fri Dec 15, 2006 5:24 am |
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Guest
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Roman Bystrianyk wrote:
Quote: "U.S. breast cancer rates down by 7 per cent", Globe and Mail, December
14, 2006,
Cancers take years to form, so going off hormones would not instantly
prevent new tumours. But tumours that had been developing might stop
growing, shrink or disappear so they were no longer detected by
mammograms, doctors theorized.
Or. more likely, they develop more slowly. That would show as a sharp
immediate dip in the statistics but would bounce back somewhat in
following years. Some cases would be truly prevented, others just deferred.
Tim Jackson |
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