Breast Density Determines Breast Cancer Risk

Patients that suffer from a very early form of breast cancer and have high mammographic density, risk subsequent breast cancer, mostly at the other breast, according to researchers at Kaiser Permanente of Northern California.

A previous study concluded that patients with ductal carcinoma in situ, or DCIS, along with high breast density, had between two and three times more risks of developing a second breast cancer.

Laurel A. Habel, PhD, research scientist at Kaiser Permanente's Division of Research, and colleagues wanted to confirm these findings an carried out a larger study, on 935 women.

The patients were diagnosed with DCIS and treated with breast-conserving surgery between 1990 and 1997, at Kaiser Permanente of Northern California.

The scientists looked at medical records, analyzed mammograms at diagnosis and calculated the risk of subsequent breast cancer during the follow-up period.

They concluded that the risk of a second breast cancer was really high among women who had a higher density.

Habel said that “while risk was elevated for both breasts, the increase was greatest and most consistent for the breast opposite to the one with the initial cancer.”

Of the 935 patients, 164 had consequent ipsilateral breast cancer (cancer on the original affected breast) and 59 had a new cancer in the other breast.

Mammographic density is the proportion of the breast which looks dense on the mammogram, and it is one of the highest risks for primary invasive breast cancer.

On the mammogram, non-dense tissue looks dark gray, as it is mostly fat, while dense tissue looks white, being an area mainly containing breast ducts and connective tissue.

Laurel A. Habel insisted that further studies are necessary to really confirm these risks and see if there are ways of evaluating risks and finding other treatment options.

She said that “information on mammographic density may help with treatment decisions for ductal carcinoma in situ patients.

“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.”

The results of the study are published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.