More Breast Screening Benefits
Mammography frequently detects non-invasive tumors
WEDNESDAY, Oct. 16, 2002 (HealthDayNews) -- Approximately one in every 1,300 mammograms will result in a diagnosis of ductal carcinoma in situ (DCIS), a type of non-invasive tumor that makes up roughly 20 percent of breast cancers detected by screening, says new research.
A study in today's issue of the Journal of the National Cancer Institute found that 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 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.
Non-invasive tumors are those that have not spread into the breast tissue and are contained within the cells lining the milk ducts.
The researchers, Virginia L. Ernster, of the University of California, San Francisco, and Rachel Ballard-Barbash, of the National Cancer Institute, found that the percentage of screen-detected breast cancers that were DCIS decreased with age.
For example, in women between the ages of 40 and 49, 28.2 percent of screen-detected breast cancers were DCIS; in women 70 to 84, 16 percent of screen-detected breast cancers were DCIS.
However, the rate of DCIS diagnoses per 1,000 mammograms increased with age, from 0.56 per 1,000 for women ages 40 to 49 to 1.07 per 1,000 for women ages 70 to 84. Further analysis revealed that mammograms were more sensitive at detecting DCIS than they were for detecting invasive breast cancer or tumors that have spread into the breast tissue.
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.
An overview on DCIS can be found here.