A Better Detector of Breast Cancer

Researchers at Duke Medical Center have developed a new breast scanner designed to detect subtle changes in breast cells before a lump can be felt by hand or seen with X-ray mammography.

Such early detection should help doctors treat breast cancer before it has formed a tumor or spread to lymph nodes, says Martin Tornai, associate professor of radiology and biomedical engineering and developer of the device. The new camera has undergone extensive testing in artificial breasts and will be tested on women beginning this spring.

The camera uses nuclear medicine to pick up chemical changes to breast cells that signal that the cells are becoming malignant, says Tornai. The camera should be particularly useful for detecting tumors in large or dense breasts, which are difficult to image using traditional mammography because X-rays often cannot penetrate them. The new device is also able to image small breasts and the nearby chest wall and can even image the auxiliary lymph nodes to look for evidence of metastasis, which traditional mammography cannot do. It works without any breast compression, and women may not be required to remove their bras.

The key to the new scanner is that it detects changes in the behavior of cancer cells, rather than structural changes such as tumor masses, which take much longer to develop, says Tornai. "Once you start seeing structural changes using mammography, that indicates the molecular process has been going on for awhile," he says. "If we can detect subtle changes in cells before a tumor has developed, we have a better chance of treating the abnormal cells in their earliest stages of malignancy."

To use the device, a cancer-specific radioactive tracer is injected into the patient's bloodstream. The tracer, called sestamibi, is "preferentially" absorbed by cancer cells, because they have large numbers of mitochondria, the cells' powerhouses. Cancer cells have more mitochondria than normal cells because they are more metabolically active and require more energy to grow and spread.

The camera obtains an image by picking up gamma rays--high-energy photons or units of light--that are emitted by the radioactive atom attached to sestamibi. The gamma rays easily penetrate the tissue and can be detected noninvasively by a gamma- ray camera.

"Nuclear imaging tracers like sestamibi show up in both pre-malignant and malignant breast cells as a little light bulb in the middle of a dim space," says Tornai. "You really want a tracer to home in on small bits of cancer that may otherwise be too small for other scanners to detect."

Gamma-ray tracers such as sestamibi have a short half-life and are broken down quickly by the liver and excreted. The amount of radiation exposure from a single diagnostic procedure is about the same as a year's exposure from the natural background radiation found in the environment, says Tornai; hence, they are relatively safe.

"This technology could potentially be applied to screening women who are at high risk for breast cancer, particularly younger women who have denser breast tissue," he says.

Tornai plans to begin imaging studies with patients at Duke this spring and will begin studies with physicians to determine the smallest lesion that can be detected with the naked eye from the resulting images.