Sentinel lymph nodes are those lymph nodes where fluid from a specific part of the body arrives first. Metastases from tumors in that specific part of the body will also end up in these sentinel lymph nodes. By removing the sentinel nodes and having them examined (this is called a sentinel lymph node procedure), a doctor can determine whether there are very small metastases in the lymph nodes. This is important to know for the tumor stage and further treatment.
Visual detection of sentinel lymph nodes
Which lymph nodes are sentinel lymph nodes varies per location of the tumor. To detect them, a slightly radioactive liquid is injected around the tumor before surgery and a scan is made to determine the location of the sentinel lymph nodes. During the operation the surgeon can also track in which lymph nodes the liquid accumulates with a special detector (called a gamma probe): those are the sentinel lymph nodes.
In addition, a blue dye can be injected so that the lymph nodes are also visually detectable during surgery. However, the blue dye stains only 60% of the sentinel lymph nodes, and can sometimes cause an allergic reaction. In adults, the use of a fluorescent agent, indocyanine green (ICG), as replacement for the blue dye, appears to be a safe, sensitive method for visual detection of sentinel lymph nodes.
Bernadette Jeremiasse, physician-researcher in prof. dr. Marc Wijnen's group at the Máxima center, investigated whether ICG can also be safely used in children who need a sentinel node procedure. To this end, she collaborated with colleagues at the UMC Utrecht and the Antoni van Leeuwenhoek in Amsterdam. The researchers coupled the fluorescent agent ICG with the routinely used slightly radioactive agent. This coupled agent was injected prior to surgery in a total of 15 children with cancer (melanoma, squamous cell carcinoma or sarcoma) who participated in the study.
Easy to use and helpful
Before surgery, using an infrared camera, the researchers saw sentinel lymph nodes through the skin by green fluorescence in 10 out of 15 children. During surgery, 95% of the sentinel nodes were visible with fluorescence, and 100% with radioactivity. The fluorescent agent did not cause any side effects in the children. According to the surgeons, this method was easy to use and helpful in detecting sentinel lymph nodes. Therefore, the researchers concluded that this method is feasible and can be safely used in children. This method will be used at the Máxima center from now on.