PRESS RELEASE: Mammography Frequently Detects Noninvasive Tumors
Approximately one in every 1,300 mammograms will result in a diagnosis
of ductal carcinoma in situ (DCIS), and this type of noninvasive
tumor makes up roughly 20% of breast cancers detected by screening
mammography, according to a study in the October 16 issue of
the Journal of the National Cancer Institute.
As the use of screening mammography has increased, the detection
of DCIS--which usually cannot be felt by a clinical exam--has
also risen. But because the lesions are removed when detected,
doctors are uncertain what percentage of such lesions, if untreated,
would progress to invasive breast cancer. Studies have shown
that only a fraction of women with DCIS treated by lumpectomy
(removal of the lump) alone later progress to invasive cancer.
Thus, there is a concern that diagnosis and treatment of many
DCIS cases may not be beneficial.
To determine the frequency of DCIS detection in screening mammography,
Virginia L. Ernster, Ph.D., of the University of California,
San Francisco, and Rachel Ballard-Barbash, M.D., of the National
Cancer Institute, and their colleagues linked mammography data
from 540,738 women between the ages of 40 and 84 to population-based
cancer and pathology registries. The authors then calculated
the percentage of screen-detected breast cancers that were DCIS
and the rate of DCIS per 1000 mammograms.
They found that approximately 20% of the breast cancers detected
by screening mammography were DCIS and that the overall rate
of DCIS detected by mammography was approximately 1 in every
1,300 mammograms. They also found that the percentage of screen-detected
breast cancers that were DCIS decreased with age.
in women aged 40 to 49, 28.2% of screen-detected breast cancers
were DCIS whereas in women aged 70 to 84, 16% of screen-detected
breast cancers were DCIS. However, the rate of DCIS diagnoses
per 1000 mammograms increased with age, from 0.56 per 1000 for
women ages 40 to 49 to 1.07 per 1000 for women ages 70 to 84.
Further analysis revealed that mammograms were more sensitive
at detecting DCIS than they were for detecting invasive breast
The authors point out that the likelihood of benefit from treatment
of DCIS is probably greater for women with larger, higher grade
lesions than for those with very small, low-grade lesions.
the uncertainty about the natural history of DCIS, the clinical
significance of screen-detected DCIS needs further investigation,"
the authors conclude.
[10/16/2002; Journal of the National Cancer Institute]
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