SAN FRANCISCO - Electrical impedance scanning (EIS) may help sort out which premenopausal women need additional imaging studies to rule out breast cancer, according to a presentation this week at the American College of Obstetrics and Gynecology (ACOG) meeting.
The developers of EIS hope the technology will increase diagnostic accuracy among young women with denser breasts, according to Dr. Ron Ginor, president and CEO of Austin, TX-based Mirabel Medical Systems. He stressed that EIS is not being tested on postmenopausal women, and that it is not intended to replace screening mammography.
However, in premenopausal women, it may fill a gap between doing nothing or subjecting them to anxiety-producing workups when a suspicious lesion is found, or when they have a family history of early breast cancer.
"The biological basis of EIS is the electrical signal changes we see in breast cells," explained principal investigator Dr. Alexander Stojadinovic. The signal change occurs early in the carcinogenesis process, he added. Stojadinovic is the vice chairman of surgery at Walter Reed Army Medical Center in Washington, DC.
When undergoing EIS, the patient holds a cylinder that serves as a ground. Another instrument is held sequentially over the nine segments of the breast, including the nipple, creating an electrical circuit with the cylinder. The data are fed into a computer and create an image on the computer screen.
The system's binary algorithm categorizes findings as either normal or suspicious. In the current research, women with suspicious findings underwent additional diagnostic work with three imaging modalities: diagnostic mammography, ultrasound, or MRI.
The investigators recruited 1,163 women, age 40 or younger. They then separated the women by risk group to determine EIS's specificity and sensitivity. To determine the system's specificity, they analyzed the results in 601 women, who had been determined to have no elevated risk of breast cancer. In those women, 578 had normal findings, for a specificity of 96.2%.
In the 562 women who had an elevated risk, the team classified them into six categories:
- Group 1: 253 with no suspicious lesions, who had no follow-up imaging
- Group 2: 200 whose results showed that further imaging was required, but who had no abnormalities
- Group 3: 16 who had at least one benign lesion found on follow-up imaging but no biopsy
- Group 4: 84 who had a low-risk benign lesion confirmed by biopsy
- Group 5: Six who had a high-risk benign lesion
- Group 6: Three who had a confirmed carcinoma
The sensitivity of a positive EIS result was linked to the categories' increasing risk as follows: 2.8% in group 1, 2.0% in group 2, 6.0% in group 3, 5.0% in group 4, 33.3% in group 5, and 66.7% in group 6 (p < 0.001).
The overall sensitivity was 33%, Stojadinovic said, about twice as high as conventional screening mammography alone. A woman with a positive EIS result was seven times more likely to have breast cancer than a woman in the general population, the study showed.
No one particular imaging modality is preferred for follow-up imaging, Stojadinovic stressed, adding that EIS is still investigational and that the manufacturer is going through the series of clinical trials required for FDA approval for screening in premenopausal women.
By Paula Moyer
AuntMinnie.com contributing writer
May 12, 2005
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