Magnetic seed markers safe and effective for nonpalpable breast lesion localization in Chinese women

A retrospective review of a pilot study in Chinese women who underwent magnetic seed marker–guided breast lesion excision reports >90 percent success rate and no complications.

“With the increasing use of screening mammography and advances in neoadjuvant therapy, surgery is more often performed on nonpalpable tumours. Accurate image-guided localization is the key to successful excision of these lesions,” wrote the researchers. [Hong Kong Med J 2007;13:106-113; Hong Kong Med J 2016;22:202-209; N Engl J Med 2016;375:1438-1447]

However, conventional techniques, such as hookwire and radioguided occult lesion localization (ROLL), have multiple inherent limitations and challenges. Wire placement must be done on the day of surgery to minimize the risk of wire dislodgment, limiting scheduling flexibility. Furthermore, the surgical approach is limited by the wire track, potentially affecting cosmetic outcomes. [Radiol Clin North Am 2017;55:591-603; Radiographics 2019;39:1886-1906; Br J Radiol 2018;91:20170740] ROLL also needs to be performed on the same day as or the day before surgery due to the half-life of the radiotracer. Moreover, radiation safety precautions and the need for Nuclear Medicine unit support limit its widespread use. [Clinics (Sao Paulo) 2011;66:1003-1007; Clin Nucl Med 2017;42:e498-e503]

Of 21 patients (mean age, 60 years) included in the current study, 13 patients had one magnetic seed marker placed on the day of surgery, while eight had magnetic seed markers inserted before (median, 8 days) surgery in an outpatient setting. The most common type of target lesion was solid mass (15 out of 21 patients), all of which had markers placed under ultrasound guidance. The other six lesions had magnetic seed markers placed by stereotactic guidance, including three groups of microcalcifications, one biopsy marker, one architectural distortion, and one focal asymmetry. One group of calcifications required two magnetic seed markers for bracketing due to its extensive distribution. [Hong Kong Med J 2020;26:500-509]

“Placement success was achieved in 20 of 22 magnetic seed markers, with a success rate of 90.9 percent. The mean final target-to-seed distance was 3.1 ± 9.8 mm,” reported the researchers. “All 22 magnetic seed markers could be localized by the probe intraoperatively and removed successfully.”

Two magnetic markers (9.1 percent) placed under stereotactic guidance migrated ≥10 mm away from their targets. As a result, two out of 21 lesions required alternative localization on the day of surgery to guide excision. “One of the lesions was a mammographic architectural distortion that could be visualized on ultrasound,” noted the researchers.

Magnetic seed marker–guided excision was performed on 19 lesions as planned, with a mean sonographic depth of magnetic seed markers from skin of 10.8 ± 4.8 mm (range, 3–21 mm). “Due to limitations of signal transmission, magnetic seed markers are intended to be placed at a depth ≤3 cm from skin according to the manufacturer’s instructions. The depth limitation of magnetic seed markers is probably not a major issue in the Chinese population, since Chinese females tend to have thinner breasts,” proposed the researchers. [https://www.endomag.com/magseed/overview/; Int J Epidemiol 2001;30:959-965]

“The magnetic seed marker system was introduced in Hong Kong in 2019 and has demonstrated safety and efficacy in localizing and excising nonpalpable breast lesions in Chinese women. As it appears to overcome many of the limitations of conventional localization techniques, it can be used as an alternative to hookwires or ROLL in selected patients,” concluded the researchers.