Although high mammographic breast density is associated with an increased risk of developing cancer, it does not appear to increase the risk of death among breast cancer patients, according to the results of a study published in the Journal of the National Cancer Institute.
Breast cancer is the most commonly diagnosed type of cancer (other than skin cancer) in US women. Each year, roughly 227,000 women are diagnosed with breast cancer and close to 40,000 die of the disease.
Breast density refers to the extent of glandular and connective tissue in the breast. Breasts with more glandular and connective tissue—and less fat—are denser. Breast density can be assessed by mammography.
Women with higher breast density are at increased risk of developing breast cancer, but less information has been available about the relationship between breast density and breast cancer prognosis.
To examine the relationship between breast density and breast cancer mortality, researchers analyzed data from the Breast Cancer Surveillance Consortium (BCSC), a population-based registry of breast imaging facilities in the United States. They limited their data to five BCSC registries that consistently collect data on body mass index (BMI) in order to adjust for confounding factors. The study included 9,232 women diagnosed with invasive breast cancer at age 30 or older between 1996 and 2005. The patients were followed on average for 6.6 years. There were 1,795 deaths during follow-up, including 889 from breast cancer.
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After adjusting for other health factors, the analysis indicated that breast cancer patients with high-density breasts did not have a higher risk of death from breast cancer than patients with lower density breasts. In evaluating subsets of patients, the researchers found specific subgroups that had an increased risk of breast cancer death associated with lower breast density—especially among obese patients.
The researchers concluded that high mammographic breast density—a strong risk factor for the development of breast cancer—was not associated with an increased risk of death from the cancer. They speculated that the risk factors for the development of breast cancer may not be the same as the risk factors associated with mortality from breast cancer.
Gierach GL, Ichikawa L, Kerlikowske K, et al. Relationship between mammographic density and breast cancer death in the breast cancer surveillance consortium. Journal of the National Cancer Institute. 2012; 104 (16): 1218-1227.
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