Lymph Node Harvesting in Colorectal Cancer: The Role of Fluorescence Lymphangiography
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Lymph node harvest in colorectal cancer surgery is an independent prognostic factor and has implications on staging and adjuvant therapy. Ensuring the entire lymphatic basin of a tumor is included in the resection margins is of particular concern in colon cancer, where consensus on optimal resection technique, akin to total mesorectal excision in rectal cancer, is lacking.
Intraoperative lymphangiography using fluorophores such as indocyanine green (ICG) can be used to map lymphatic basins in colorectal cancer, with far-reaching potential implications including guiding mesocolic resection margins, tailoring pelvic sidewall clearance in rectal cancer, and targeting sentinel nodes for detailed immunohistochemistry to enhance staging accuracy. Though a relatively new application of fluorescence, ICG lymphangiography has shown itself to be a safe and feasible technique in lymphatic mapping, with benefits in sentinel node identification over conventional techniques.
Optimization of the technique is required; currently a standardized protocol for ICG administration is lacking, and factors impacting the accuracy of fluorescence lymphangiography must be further elucidated. Addressing these limitations with larger, prospective trials, alongside investigation of new techniques such as conjugation with cancer-specific ligands, could render this an exciting technique in colorectal cancer surgery.
KeywordsLymphangiography Fluorescence Colorectal cancer Indocyanine green
Lymphatic mapping may be demonstrated using an extra- or intracorporeal technique. The technical aspects remain the same whereby ICG is mixed in 20 mL of sterile water and injected into the sub-serosal space. Four areas are selected around the tumor, and 1 mL of the diluted ICG is carefully injected ensuring not to spill excess ICG in the operating field. During the extracorporeal technique, an alcohol swab may be used to wipe away the excess. Once the ICG has been injected, a dark bleb is seen. When using the intracorporeal technique, a connector tubing set is attached to the fine “butterfly” needle. The flanges of the butterfly are cut off to allow it to be dropped into the abdominal cavity through a 5 mL port. The needle is carefully positioned into the subserosal space and a bleb raised. Again, this is repeated to surround the tumor. Lymphatics can be clearly visualized within 5 minutes although the ICG will remain in the mesentery for the duration of the surgery. There is rarely, if ever, a need to give additional interstitial injections. However, it is worth noting that thick fatty mesentery, locally advanced tumors, and challenging dissections can contribute to reduced visualization of the fluorescent lymphatics. (MOV 284894 kb)
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