TORONTO, Canada--The benefits of annual mammography screening
for women aged 50 and over are undisputed, but experts are still
polarized over whether the screening procedure is worthwhile for
women aged 40 to 49.
Prominent specialists debated the issue at a controversy session
at the annual meeting of the American Association for Cancer Research
(AACR), with one researcher suggesting that development of tests
to improve interpretation of the ambiguous mammograms often seen
in younger women could someday render the discussion moot.
Possible Risks of Screening
Making the case against mammography screening for women in their
40s was Karla Kerlikowske, MD, a primary care physician and epidemiologist
at the University of California, San Francisco.
In her analysis of 13 international breast cancer studies (JAMA,
January 11, 1995), Dr. Kerlikowske found that regular mammography
screening did not significantly decrease breast cancer mortality
among women aged 40 to 49.
She informs her patients in this age group that there is no proof
that mammography decreases breast cancer deaths and that there
are risks to undergoing screening, such as the possibility of
inconclusive tests and the risk of unnecessary diagnostic tests
that cause anxiety and discomfort.
"For a 40-year-old woman who elects annual screening for
10 years, I tell her that she has a 25% chance of having an abnormal
mammogram during those 10 years. There is a 23% chance of a false
positive, and a 6% to 7% chance of biopsy. But the chance of cancer
being detected is only 1.5%," she said.
Because of the large numbers of ambiguous, inconclusive mammograms
and false positives, many women must undergo additional expensive
tests. "It's estimated that thousands of unnecessary biopsies
are performed each year. And all of this causes distress in patients,"
Dr. Kerlikowske said that up to 40% of women who have abnormal
mammograms will have anxiety for 3 months. The small group that
needs to undergo biopsy may have anxiety for up to 18 months.
And in that group, the anxiety may persist even after the woman
learns that she has nothing to worry about.
She is also concerned about the false reassurance resulting from
a false-negative mammogram. She fears that a woman who detects
a lump after a normal mammogram may not seek further screening.
Virginia Ernster, PhD, of the University of California, San Francisco,
who moderated the debate, is herself a woman in the disputed age
group. She has elected not to have annual mammograms.
There is nothing magical about age 50, she said. She suggested
that regular screening could start earlier or later, depending
on menopausal status, but "physicians may find it easier
to ask a woman her age than her menopausal status."
The Case for Screening
Coming out firmly in favor of early screening to aid detection
was Edward A. Sickles, MD, a radiologist at the University of
California, San Francisco. Recent reports suggest an 8% drop in
breast cancer mortality for Caucasian women 40 to 49 years old,
he said, and mammography may be partly responsible.
As for the existing data suggesting that screening is not beneficial
in this age group, he contends that the studies may be statistically
invalid for younger women because breast cancer mortality is so
low in this age range.
He added that the most recently published compilation of international
breast cancer studies, using, he said, more recent data than those
presented by Dr. Kerlikowske, shows a statistically significant
24% reduction in breast cancer mortality for mammography screening
of women aged 40 to 49 (Smart CR et al: Cancer, April, 1995).
Dr. Sickles noted that mammography may be discouraged in this
age group because the denser breast tissue of younger women can
obscure tumors and make the procedure less accurate. But he thinks
this argument is negated by improvements in mammography techniques
that allow physicians to "see more in the images," he
To Dr. Dutzu Rosner, of the State University of New York at Buffalo,
the answer to the question of mammography in the 40s is really
improved adjunctive imaging techniques that would help physicians
interpret ambiguous mammograms in this age group.
Dr. Rosner and his team are studying a radioactive isotope attached
to a monoclonal antibody that zeros in on breast tumors. Dr. Rosner,
who presented his research at the conference, believes that this
method could be an important back-up to ambiguous mammograms.
To date, in the studies at Buffalo, radioimmunodetection has proven
83% to 100% accurate in predicting which ambiguous mammograms
are not breast cancers, depending on the type of monoclonal antibody
He cautioned that the results are very preliminary, with only
19 women studied so far. However, he said, these results are similar
to those reported in January in a European study, which found
no false-positive tests in 31 women studied.
A paper describing the Buffalo study has been accepted by Cancer
Investigation, he said, and is scheduled for publication in the
fall of this year.