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DURHAM, N.C. -- The 56-year-old woman was relieved: her mammogram showed no signs of breast cancer. Just two weeks later at a follow-up exam, a magnetic resonance image illuminated a glaring mass the size of a walnut. The tumor was cancerous, and its detection demonstrated all too clearly the disparity between two imaging techniques – x-ray mammograms versus magnetic resonance imaging (MRI) -- that have opposing strengths and weaknesses.

Mammograms – long the gold standard for detecting breast cancers – work best in women whose breast tissue is not dense. Dense breasts with tightly packed cells can block the X-rays from distinguishing a cancer mass from other packed cells. Yet MRIs are 10 times more costly and fail to show "calcifications" – small deposits that can predict the later onset of breast cancer. Minority women of color are at particular risk of undetected breast cancers because they tend to have denser breasts – and little if any data exist as to how best to screen them for cancer, said researchers from the Duke Comprehensive Cancer Center's Breast Health Clinic.

Deciding which woman will benefit most from a given breast cancer screening technique is key to ensuring that cancers do not go undetected, said Victoria Seewaldt, M.D., director of Duke's Breast Health Clinic.

"It is critical that all high-risk women of color have access to MRI because they often have dense breast tissue and mammograms can miss breast cancers in this situation," said Seewaldt.

Mammograms detect tumors in only 33 percent of women with dense breast tissue, she said. MRIs detect tumors in 80 percent of women. Yet MRI exams are very expensive – about $1,200 – and insurance companies are hesitant to pay the added cost without proof of the technology's benefit, she said.

"Given limited health care resources, we need to figure out how we can best use MRI screening to benefit the greatest number of women," said Seewaldt.

Her latest study is designed to address this question. African American women at high risk for breast cancer are invited to participate in a breast MRI screening trial. The outcomes of their scans will be compared to women of color who are the same age and risk level but who received only mammograms. The research team will then assess the difference in tumor detection rates. The data will also help justify why insurance companies should pay the higher cost of MRI scans for women of color and other high risk-women with dense breast tissue.

"Women of color have a greater likelihood of dying from breast cancer than do Caucasian women," said Seewaldt. "One important reason for this increased mortality is lack of access to breast cancer screening. Our goal is to improve access to new technologies such as MRI for high-risk women of color and, in doing so, reduce breast cancer mortality for all women."

In addition to improved imaging techniques, Seewaldt's team is using a novel screening technique called random fine needle aspiration to detect abnormal and malignant breast cells in women of color as well as Caucasian high-risk women. The new technique, being tested at Duke and select sites nationally, can identify specific molecular changes that often precede breast cancer. It is especially useful for detecting changes in dense breasts because each cell is analyzed individually for molecular changes that would not appear on a mammogram or MRI. Moreover, the test enables researchers to track whether individual women are responding to preventive agents.

"As scientists, we need to identify the early changes inside breast cells that progress to become cancer as opposed to those changes that are benign," said Seewaldt. "The earlier we can detect these changes, the better we can prevent them from becoming cancer.