Compared with breast-cancer patients who have nondense tissue, those with dense tissue are at significantly elevated risk of developing a tumor in the opposite breast.
That’s according to a study conducted at the University of Texas MD Anderson Cancer Center and published online Jan. 30 in Cancer.
Carlos Barcenas, MD, MSc, and colleagues reviewed the cases of 229 cancer patients who had developed contralateral breast cancer (CBC) and compared their records with those of 451 controls who did not develop CBC.
They categorized each patient’s mammographic breast density, assessed at the time of first breast-cancer diagnosis, as “nondense” or “dense” in accordance with the American College of Radiology’s characterizations for each.
They used multivariable conditional logistic regression models for statistical analysis.
Their key finding: After adjustment for potential prognostic risk factors for breast cancer, the odds of developing CBC proved significantly higher for patients with dense breasts (odds ratio, 1.80; 95 percent confidence interval, 1.22-2.64 [P<.01]) than for those with nondense breasts.
The team also observed that, among the cancer cases, 39.3 percent had nondense breast tissue and 60.7 percent had dense breast tissue. Among the controls, 48.3 percent had nondense breast tissue and 51.7 percent had dense breast tissue.
Patients who received chemotherapy or endocrine therapy were less likely to develop CBC, the authors report.
“In women with primary breast cancer, mammographic breast density appears to be a risk factor for the development of contralateral breast cancer,” the authors conclude.