One in five cancers detected by mammography is noninvasive, UCSF study finds

Of cancers detected by screening mammography, approximately 20 percent are ductal carcinoma in situ (DCIS), a non-invasive tumor contained within the walls of the breast duct, according to a multi-state study led by UCSF researchers. The researchers found that the likelihood of DCIS diagnosis increases with age and, overall, one in every 1300 screening mammograms results in a diagnosis of DCIS.

“More research is needed to understand the biology of DCIS to help us identify which disease is likely to progress to invasive cancer, and also to better tailor treatment,” said Karla Kerlikowske, MD, UCSF associate professor of medicine and epidemiology and biostatistics.

Kerlikowske, who is also director of the Women Veterans Comprehensive Health Center at the SFVAMC, is among the authors of the study which was led by Virginia Ernster, PhD, UCSF professor emeritus of epidemiology and biostatistics. The findings were published in the October 16 issue of the Journal of the National Cancer Institute.

Mammography has become a very common health screening practice: an estimated 28.4 million US women had mammograms in 1998. As screening mammography has become more common the incidence of diagnoses of DCIS has increased, the authors said.

Pathologists categorize DCIS by size and cellular features including nuclear grade, from low to high. It is almost always treated with surgical excision of the tumor, whether by lumpectomy alone, lumpectomy followed by radiation or by mastectomy. The authors noted that some women likely benefit from having DCIS detected and treated while others may not, depending on whether the disease is likely to progress. “The benefit of detection is probably greater for women with larger, high-grade lesions,” Ernster said.

Ernster and her colleagues used clinical records from 540,738 women age 40 to 84 who underwent screening mammograms throughout 1996 and 1997. They linked those data with population-based cancer and pathology registries in seven states. They calculated that 3266 cases of breast cancer were detected as a result of mammography. Of those, 2675 were invasive and 591 were DCIS.
Although the proportion of all breast cancers detected that were DCIS was higher in women ages 40-49 than in older women, the actual rate of DCIS per 100,000 women having mammograms increased with age.

An estimated 203,500 women in the US will be diagnosed with invasive breast cancer in 2002 and approximately 39,600 will die of the disease during the year.

Breast cancer is the second leading cause of cancer death in women, however, according to the American Cancer Society, mortality rates declined significantly between 1992-1998. The Society attributes the decline to both earlier detection and improved treatment.

## The study was funded by the National Cancer Institute. Additional authors on the paper are:

* R. Ballard-Barbash, Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, MD;
* W. E. Barlow, Center for Health Studies, Group Health Cooperative, Seattle, WA, and Department of Biostatistics, University of Washington, Seattle;
* Y. Zheng, Department of Biostatistics, University of Washington;
* D. L. Weaver, (Department of Pathology), B. M. Geller (Health Promotion Research), University of Vermont, College of Medicine, Burlington, VT;
* G.  Cutter, Center for Research Design and Statistical Methods, University of Nevada, Reno;
* B. C. Yankaskas, Department of Radiology, University of North Carolina, Chapel Hill;
* R. Rosenberg, Department of Radiology, University of New Mexico, Albuquerque;
* P. A. Carney, Norris Cotton Cancer Center/Dartmouth-Hitchcock Medical Center/Department of Community and Family Medicine, Dartmouth Medical School, Lebanon, NH;
* Department of Epidemiology and Biostatistics, School of Medicine, and General Internal Medicine Section, Department of Veterans Affairs, University of California, San Francisco;
* S. H. Taplin, Center for Health Studies,Group Health Cooperative, Seattle; and
* N. Urban, Fred Hutchinson Cancer Research Center, Division of Public Health, Seattle.