- Breast cancer patients or survivors with denser breast tissue have an increased risk of developing cancer in the contralateral breast.
- Though denser breast tissue is a known risk factor for primary breast cancer, its association with secondary breast cancer has so far, not been well-established.
- The findings have implications for both newly diagnosed patients with dense breasts and for breast cancer survivors to manage their long-term risk of secondary diagnosis.
Breast cancer patients who have a denser breast tissue have almost a two-fold increased risk of developing disease in the contralateral breast.
The findings according to new research from The University of Texas MD Anderson Cancer is among the first to find the association between breast density (BD) and contralateral breast cancer (CBC).
‘Breast cancer patients with denser tissue have a two-fold increase in the risk of developing cancer in the other breast compared to patients who do not have denser breast tissue.’
"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," said study author Isabelle Bedrosian, M.D., associate professor, Breast Surgical Oncology.
"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." Bedrosian added.
The estimated 10-year risk for women with breast cancer developing CBC can be as low as 2% or as high as 40%
. This difference is due to the variability of risk factors across the patient population.
Researchers conducted a retrospective, case-controlled study, with 680 patients who had stage I, II and III breast cancer. Patients were being treated at MD Anderson between 1997 and 2012.
From the study, patients with BRCA mutations were excluded due to their increased risk of causing CBC.
Cases comprised of 229 women with an additional diagnosis of metachronous CBC, which is defined as breast cancer in the opposite breast diagnosed more than six months following the detection of the first cancer.
Controls comprised of 451 patients who had not developed CBC.
The 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, M.D., assistant professor, Breast Medical Oncology, and the study's corresponding author.
The breast density of each patients was assessed using mammogram reading at the time of first diagnosis, and categorized as "nondense" or "dense," according to 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.
Among the controls 48.3% had nondense breast tissue and 51.7% had dense breast tissue.
The findings revealed an almost two-fold increase in the risk of developing CBC 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 Barcenas. "Our future goal is to develop a risk model incorporating breast density to best assess a breast cancer survivor's risk of developing CBC."
A major challenge in the management of this patient population, is trying to counsel women appropriately on their risk of developing breast cancer in the other breast.
In future, researchers can use this information to counsel patients and guide them on options for treatment and surveillance, if their risk factors are high.
The study, is published in the journal Cancer
- Isabelle Bedrosian et al. Mammographic breast density is associated with the development of contralateral breast cancer. Cancer; (2017) DOI: 10.1002/cncr.30573