Screening Mammography for Forty-Something Women: New Analysis
Emphasizes Benefits of Yearly Exams
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Screening Mammography for Forty-Something Women: New Analysis
Emphasizes Benefits of Yearly Exams |
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2000/10/10 -
Background
Reference Information: Current
interpretations of trial experience and community screening programs
suggest that annual mammography is likely to be more effective for the
early detection of breast cancer in women between 40 and 49 years of age
than screening that is conducted at longer intervals, according to Robert
A. Smith, PhD. Although the value of screening mammography for women
younger than 50 has been the subject of intense, and sometimes
contentious, debate over the past two decades, Dr. Smith believes that the
evidence for annual screening is now clear. Writing in
the September/October issue of CA—A Cancer Journal for Clinicians,
Dr. Smith, who is Director of Screening for the American Cancer Society,
Atlanta, GA, observed that tumors found in women younger than 50 tend to
progress at a faster rate, often change more readily from a lower to a
higher grade of malignancy, and spread to lymph nodes more quickly than
those discovered in women 50 years of age or older. Moreover,
the preclinical detectable phase—which is when a small tumor has already
developed and is detectable by mammography but is not yet palpable—is
shorter in women between 40 and 49 compared with their older counterparts. "Evaluation
of survival according to tumor characteristics demonstrates that breast
cancer is not an inherently different disease in women younger than 50
compared with older women," Dr. Smith explained. "Nevertheless,
evidence about tumor progression rates indicates that shorter screening
intervals are required in younger women to detect tumors at a favorable
stage during the preclinical phase." Based on
his extensive review of the literature and a detailed evaluation of the
complex factors involved, Dr. Smith and other experts suggest that for
women younger than 50, annual (as opposed to biannual) screening
mammography is likely to be more effective for identifying early tumors
while they are still highly curable. A Canadian
research group recently reported that, for women in their fifties,
self-breast examination plus annual clinical breast examination were
roughly equivalent to annual screening mammography alone with respect to
preventing breast cancer deaths. Although this controversial study focused
on women 50 years of age and older, and Dr. Smith’s article discussed
women in their forties, he reconfirmed that the "American
Cancer Society remains committed to the efficacy of mammography in women
40 and older and stands by its guidelines." For women with
average risk of breast cancer, the ACS guidelines recommend monthly
self-breast examination starting at age 20, clinical breast examination
every three years between the ages of 20 and 39,and yearly clinical breast
exams and mammography starting at age 40. Noting
that the Canadian study had been criticized for problems with
randomization, poor quality mammograms, and lack of properly trained
radiologists, Dr. Smith also pointed out that this was the only
study that found higher rates of lymph-node positive breast cancers in
women who had had mammography than in those who had not. These results
would not be entirely unexpected, he said, "if you consider that the
benefit of a very high quality clinical breast exam was being compared
with poor quality mammography in a study that was also plagued with
unexplained, but clearly evident problems with study randomization. More
to the point," he added, "the findings are discordant with the
larger body of scientific research on the effect of mammography on early
breast cancer detection." The
"principal advantage of mammography is to find breast cancer when it
is very small and before the cancer has spread to the lymph nodes,"
Dr. Smith said. "Women over the age of 40should use monthly self-exam
and yearly clinical exam in addition to mammography, not as substitutes
for it," he concluded. |
