Researchers at Kaiser Permanente’s Northern California Division of Research have found that patients with a very early form of breast cancer, called ductal carcinoma in situ or DCIS, who have higher mammographic density, may be at increased risk for later breast cancer, especially in the breast opposite the one with the initial cancer.
“While risk was elevated for both breasts, the increase was greatest and most consistent for the breast opposite the one with the initial cancer,” said Laurel Habel, PhD, a research scientist at the Division and the study’s lead investigator.
Mammographic density refers to the proportion of the breast that appears dense on a mammogram; it is one of the strongest risk factors for primary invasive breast cancer.
On a mammogram, dense tissue looks white, while non-dense tissue looks dark grey. The dense area consists primarily of breast ducts and connective tissue, while the non-dense tissue is mostly fat.
The study was published in the October 2010 issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
A previous study showed that for patients with DCIS, the risk of developing a second breast cancer doubled or even tripled if they had higher mammographic density.
To confirm those findings, Dr. Habel and her colleagues conducted a new study in a larger group of women, including 935 diagnosed with DCIS. These women had been treated with breast-conserving surgery – meaning not a mastectomy — between 1990 and 1997 at Kaiser Permanente Northern California.
Researchers reviewed medical records, evaluated mammograms at diagnosis and then calculated the risk of later breast cancer events during follow-up.
Dr. Habel said additional studies are needed to confirm her team’s findings and to determine whether breast density measurement can help clinicians assess breast cancer risk and treatment options.
“Information on mammographic density may help with treatment decisions for ductal carcinoma in situ patients,” she said. “While it’s not a strong enough risk factor on its own, it may be possible to combine it with other factors to improve risk assessment and inform treatment decisions.”