One of the greatest challenges faced by oncologic surgery teams is to know exactly which tissue to remove while the patient is in surgery. A new technique has been developed that allows surgeons, during surgery, to identify which lymph nodes are cancerous so that healthy tissue can be saved.

Lymph nodes, which are located throughout the body, serve as filters that contain immune cells to fight infection and clean the blood. When cancer cells break away from a tumor, the cells can travel through the lymph system and hide in these tiny organs. Surgeons remove the nodes to determine if a cancer has spread. Human lymph nodes, however, are only a half centimeter in size and are difficult to discern among the surrounding tissue during surgery. Furthermore, even when surgeons are able to map the location of the nodes, no current technique indicates whether the lymph nodes contain cancer. As a result, more lymph nodes are removed than may be necessary.

“With molecular-targeted imaging, surgeons can avoid unnecessary removal of healthy lymph nodes which is better long term for patients,” said Quyen T. Nguyen, MD, director of the facial nerve clinic at UC San Diego Health System. “The range of the surgeon’s visual field is greatly enhanced by a molecular tool that can help achieve accurate surgical margins and detection of metastases so that no tumor is left behind.”

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Fluorescently labeled molecules, known as ratiometric activatable cell-penetrating peptides (RACPP), are injected. When used in mouse models, surgeons could see where the cancer had spread with high sensitivity and specificity even when the metastatic sites were only a few millimeters in size.

This form of instant pathology is an improvement over traditional sentinel node mapping, whereby only the location of the lymph node is detected without gleaning any information on actual cancer involvement. Current methods for managing prostate cancer and neck squamous cell carcinoma only reveal the extent of cancer involvement after the patient has undergone surgical removal of all susceptible lymph nodes.

This new technique will decrease operating room time because the surgical team need not wait for pathology reports, decrease time the patient is under anesthesia, and decrease unnecessary resection of lymph nodes that are noncancerous. These findings were published in Cancer Research (2013; doi:10.1158/0008-5472.CAN-12-2969).