SAN ANTONIO — New and better methods are needed for localizing nonpalpable breast lesions at the time of surgical excision, according to two researchers who presented preliminary data on alternative methods here at San Antonio Breast Cancer Symposium (SABCS) 2014.
Both researchers say their proposed methods, one using a magnetic tracer, and the other an electromagnetic reflector, can bypass some of the drawbacks of current wire-guided and radioisotope- guided localization methods.
"One third of breast cancer diagnosed annually throughout the world is nonpalpable, and that level is likely to increase because of the greater implementation of screening programs as well as more advanced modalities, such as MRI, which pick up more clinically occult lesions," said Muneer Ahmed, MRCS, a surgeon from King’s College London, in the United Kingdom.
Currently, the most widely used method of wire-guided localization (WGL) is seriously limited by the need for same-day wire placement and excision, and it also faces other technical challenges resulting in a re-excision rates as high as 50%, said Dr Ahmed. "So clearly there's a need to try and develop an alternative technique."
Radioisotope techniques such as radio-guided occult lesion localization and radioactive seed localization have emerged to address some of the WGL drawbacks, but they too have limitations, said Charles Cox, MD, who invented and patented the radioactive seed technique.
"The problem with radioactive material is that it's great at localizing the cancer, but it has all the regulatory issues and the fear factor of putting something radioactive into someone," said Dr Cox, a surgeon from the University of South Florida College of Medicine, in Tampa.
At the meeting, Dr Cox presented preliminary data on the SAVI Scout surgical guidance system (Cianna Medical Inc), which uses an intratumoral electromagnetic wave device, implanted under ultrasound or mammographic guidance, to localize occult breast lesions with a probe during surgery.
At the adjacent poster, Dr Ahmed's study showed preliminary results with the MagSNOLL Trial, using an iron oxide magnetic tracer (0.5 mL, Sienna, Endomagnetics Ltd) injected into occult breast lesions under ultrasound guidance up to 1 week before surgery. The tracer was then detected during surgery using a hand-held magnetometer.
In the MagSNOLL trial, among an initial 20 patients with nonpalpable lesions, the magnetic tracer technique detected 100% of lesions, with only two requiring re-excision because of positive margins, he said.
An additional benefit of the magnetic tracer is that it can also be used to localize sentinel lymph nodes (SLNs), especially when used in conjunction with patent blue dye.
Dr Ahmed’s study showed that 85% of SLNs were detected using the magnetic tracer alone, with a 97% detection rate when blue dye was also used.
In Dr Cox's trial, 24 patients underwent intratumoral placement of the electromagnetic reflector under ultrasound or mammography guidance. The reflector was placed an average of 1.1 days before surgery and was then localized in the operating room with the use of a hand piece and console to detect feedback.
Among the seven patients who underwent excisional biopsy and the 17 who underwent lumpectomy, the reflector and lesion were successfully removed.
Final pathology, which was available from 19 patients, showed benign findings in all excisional biopsy patients and clear margins in 11 of 12 lumpectomy patients. One patient had a positive margin and required re-excision.
"I would like to see this being used for any nonpalpable breast biopsy procedure," said Dr Cox. "The biggest issue is, how much is it going to cost? That will be the next big hurdle ― how to bring a new device to market and get it paid for."
The materials and devices in both studies already meet criteria for regulatory approval in their respective countries because they are already used either in breast cancer or other medical treatments.
Both investigators are planning larger studies.
Dr Cox's study was funded by Cianna Medical Inc for a total of $5000 for data collection from up to 25 patients enrolled locally. Materials were provided by the company. Materials for Dr Ahmed's study were provided by Endomagnetics Ltd. Dr Cox is a consultant and serves on the advisory board of Cianna. Dr Ahmed has disclosed no relevant financial relationships.
San Antonio Breast Cancer Symposium (2014): Abstracts P1-16-09 and P1-16-10. Presented December 11, 2014.
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Cite this: New Methods Explored to Localize Nonpalpable Breast Lesions - Medscape - Dec 11, 2014.