BY RUTHANN RICHTER
Magnetic resonance imaging (MRI) has the potential to become a powerful tool for screening women at high risk for developing breast cancer, a visiting lecturer from the University of Toronto told a Stanford audience from engineering, radiology and surgery during a presentation April 13.
In recent years, MRI has become an increasingly useful device in the diagnosis and treatment of breast cancer patients, said Stefanie Jeffrey, MD, assistant professor of surgery and chief of breast surgery at Stanford. For instance, Stanford physicians now use MRI to help evaluate the impact of preoperative chemotherapy in women with large cancers of the breast and to look for multiple tumors in some women before breast conservation surgery, Jeffrey said. Stanford doctors also use MRI to help find hidden tumors that could not be detected through other means, particularly in women with dense breast tissue or in women at risk for cancer in both breasts, Jeffrey told more than 50 faculty and students at the presentation in the Packard Engineering Building.
"There are patients behind the work that you do, and it really has helped many of them," Jeffrey told the group, which included a number of Stanford scientists who have made major contributions to the imaging field. She said Stanford remains in the forefront of breast MRI research, which is being conducted at about a dozen academic medical centers across North America.
Donald Plewes, PhD, a professor of medical biophysics and a senior scientist at the University of Toronto, described his experience using MRI to screen women considered at high risk for the disease. Plewes directs an ongoing multicenter trial that so far has compared MRI with other traditional imaging methods, including mammography and ultrasound, to screen some 176 high-risk women. The women, whose mean age was 43, were either carriers of one of the breast cancer genes -- known as BRCA1 and BRCA2 -- or had several close female relatives with breast cancer.
Using MRI, the researchers were able to identify eight out of nine cases of early breast cancer in the asymptomatic women -- the most effective method available, Plewes reported. By comparison, mammography detected only four of the nine cases, while ultrasound identified five of the nine cases. A clinical exam, in which a doctor examines the breast for possible lumps, detected only two of the nine tumors, he said.
"It certainly is encouraging in that we see cancers [with MRI] that we don't see through other imaging methods," Plewes said. "I think MRI has a very compelling role in this arena."
One of the drawbacks of the imaging technique is its high cost -- roughly $1,000 to $2,000, compared to $100 to $200 for a mammogram, Plewes said. But MRI becomes much more cost-effective when applied in a group known to be at high risk, he said.
He said some 26 percent of the women in the study indicated that they found the exam uncomfortable, largely because of the need for an intravenous line. The 45-minute test is done while the woman lies still, face down in the MRI scanner. The patient is given an injection of a contrast solution, which tends to accumulate in cancerous tissues, showing up as a bright spot on the image. The solution is harmless, and MRI generally is considered entirely safe, Plewes said.
While MRI may be useful as an initial screening tool, doctors still must perform a biopsy to confirm whether a tumor is malignant or benign, noted Bruce Daniel, MD, an assistant professor of radiology at Stanford.
"A key issue is when you find something, what do you do about it?" Daniel said after Plewes' talk.
Daniel said Stanford has eased the biopsy process through a technique that uses MR guidance to channel a wire directly to the site of a tumor. When Jeffrey and her fellow surgeons then go in to retrieve a tumor sample for biopsy, they know precisely where the lesion is located, he said. Stanford is one of a few medical centers in the country using the wire localization technique, he said. Daniel and his colleagues are also working on newer, minimally invasive methods for biopsy that would not require an open incision and a trip to the operating room, he said.
In addition, Stanford scientists are working on some technical aspects of MRI to help improve its specificity -- currently one of the major shortcomings of the imaging method. Because of its lack of specificity, MRI tends to produce more false positive test results than other imaging methods, Daniel said, forcing some women to undergo testing of tissue that turns out to be noncancerous. He said Stanford researchers already have made major technical strides that have significantly increased the resolution and speed of MRI, as well as the ability to analyze test results.
Finally, Daniel, Jeffrey and colleagues are planning to investigate the use of MR guidance in an experimental treatment for breast cancer known as radiofrequency ablation. The technique involves insertion of a needle electrode through the skin into a breast tumor. A low level of radiofrequency energy then is applied to heat and kill the tumor cells.
"You'd like to try to destroy a tumor without doing an open surgery, but it's a tricky business," Daniel said. He said clinicians want to be assured that they have not left cancerous cells behind.
The Stanford team was among the first in the world to apply the radiofrequency ablation technique in breast cancer patients, publishing results on the first five patients last October in the Archives of Surgery. In all five women, there was evidence of cancer cell death, the researchers reported.
In the next phase, the researchers
plan to test whether MRI can help define the boundaries of the
ablated zone with respect to the tumor. Their ultimate goal is to
produce even better clinical results. SR