Patients With Breast Cancer With Dense Breast Tissue More Likely to Develop Contralateral Disease
Patients with breast cancer with dense breast tissue have almost a twofold increased risk of developing disease in the contralateral breast, according to new research from The University of Texas MD Anderson Cancer Center. The study, published by Brewster et al in the journal Cancer, is among the first to find the association between breast density and contralateral breast cancer.
According to study author Isabelle Bedrosian, MD, a big challenge in the management of this patient population, especially as they are making surgical decisions, is trying to counsel women appropriately on their risk of developing breast cancer in the other breast.
“We know there are a number of well-established influences for developing both primary and secondary breast cancers, such as BRCA mutations, family history, and the tumor’s estrogen receptor status,” explained Dr. Bedrosian, Associate Professor, Breast Surgical Oncology at MD Anderson. “We also know density is a risk factor for the development of primary breast cancer. However, no one has closely looked at it as a risk factor for developing contralateral disease.”
The estimated 10-year risk for women with breast cancer developing contralateral breast cancer can be as low as 2%, and as high 40%, explained Dr. Bedrosian. The dramatic range is due in large part to the variability of risk factors across the patient population, she said.
Study Details
For the retrospective, case-controlled study, the researchers identified 680 patients with stage I, II, and III breast cancer, all treated at MD Anderson between 1997 and 2012. Patients with BRCA mutations were excluded from the study, given their known increased risk of contralateral breast cancer.
Women with an additional diagnosis of metachronous contralateral breast cancer—defined as breast cancer in the opposite breast diagnosed more than 6 months after the initial diagnosis—were the cases, and patients who had not developed contralateral breast cancer were the controls. Cases and controls were matched on a 1:2 ratio based on a number of factors, including age, year of diagnosis, and hormone receptor status.
“With our research, we wanted to evaluate the relationship between the mammographic breast density of the original disease and the development of metachronous breast cancer,” said Carlos Barcenas, MD, Assistant Professor, Breast Medical Oncology at MD Anderson, and the study’s corresponding author.
Of the selected patients, 229 were cases and 451 were controls. The MD Anderson researchers categorized each patient’s breast density by mammogram reading, assessed at the time of first diagnosis, as nondense or dense, using the categorizations from the American College of Radiology.
Among the cases, 39.3% were classified as having nondense breast tissue and 60.7% as having dense breast tissue, compared to 48.3% and 51.7%, respectively, in the controls.
After adjusting for known breast cancer risk factors, the researchers found almost a twofold increased risk of developing contralateral breast cancer in breast cancer survivors with dense breasts.
“Our findings have valuable implications for both newly diagnosed patients with dense breasts and for breast cancer survivors as we manage their long-term risk of a secondary diagnosis,” said Dr. Barcenas. “Our future goal is to develop a risk model incorporating breast density to best assess a breast cancer survivor’s risk of developing contralateral breast cancer.”
In the long-term, the researchers hope to use this tool to counsel patients on their personal risk and their options for treatment and surveillance, if their risk is sufficiently high.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
