Sentinel lymph node biopsy (SLNB) is a procedure in which the sentinel lymph node is identified, removed and examined to determine whether cancer cells are present. In breast cancer, if no cancer is detected in the sentinel lymph node, then there is no need for an axillary lymph node dissection (ALND) in which the 30 or so lymph nodes in the armpit are removed.
Locating and testing the sentinel lymph node through minimally invasive surgery is preferable to the invasive ALND and its associated problems such as nerve damage or lymphedema, and it helps to ensure that patients’ quality of life is maintained. SLNB results in shorter breast cancer operations and better patient recovery, as well as saving money and freeing up resources for healthcare providers.
Despite the advantages of SLNB, the conventional method involves injecting a radioactive tracer with or without a blue dye, and then localising the lymph nodes using a gamma probe. While effective, this method comes with significant problems:
The conventional gamma probe method is limited by the supply of a substance called molybdenum‐99, the parent radioisotope to the short‐lived gamma‐emitting technetium-99m (99mTc) used in medical imaging. Molybdenum‐99 decays so quickly that it has to be supplied to hospitals every week, and is made in just a handful of nuclear reactors worldwide.
The handling of radioactive materials is subject to stringent regulations, requiring special staff training and segregating the waste from the operating theatre.
The costs of providing and handling radioactive materials are high, so the majority of women with breast cancer will never be offered SLNB based on this method.
Competition to radioisotopes is now available. One promising technology is the use of fluorescent dyes (such as indocyanine green, ICG) in conjunction with near infrared (NIR) visualisation systems. While these fluorescent dyes are inexpensive and avoid the use of radioisotopes, the dye spreads throughout the lymphatic system and does not stop specifically at the sentinel lymph nodes. Moreover the system requires a change in working practice, as the surgeon must focus on a separate monitor, rather than the patient.
Endomag’s technology uses a magnetic tracer (Sienna+®) instead of the radioactive tracer and blue dye, and an ultrasensitive hand‐held magnetic probe (Sentimag®) rather than a gamma probe. This is the only solution that avoids the use of radioisotopes, but manages to maintain standard working practice and provide equivalent detection rates to the standard of care.