The Sentinel Node in Colorectal Carcinoma

The Lin/Rodriguez/Ota Article Reviewed

Elin R. Sigurdson, MD, PhD
Senior Member, Department of Surgery, Fox Chase Cancer Center
Daniel G. Haller, MD
Professor of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

The role of sentinel lymph node identification has been investigated over the past decade in a variety of malignancies. It has become part of standard care for melanoma. Its role in breast cancer is evolving, but with the completion of two large randomized clinical trials, it will probably be added to the surgical armamentarium for the management of most breast cancers. Studies have been proposed or are under way to evaluate sentinel node mapping in head and neck cancer, penile and vulvar cancer, and gastrointestinal cancers.

The advantage of sentinel node mapping in breast cancer and melanoma is clear. An axillary, inguinal, or cervical lymphadenectomy is associated with significant morbidity and appears to provide no benefit to the truly node-negative patient. It is easy to see why sentinel node biopsy will become the strategy of choice for identifying node-negative patients, if general surgeons can perform the procedure with acceptable accuracy.

The role of sentinel lymph node detection in other malignancies has yet to be determined. Currently in North America, many cancer patients present with involved nodes. For many other tumors, the appropriate lymphadenectomy is not associated with undue morbidity, so surgical management need not be modified for node-negative patients. For other patients, either the intraoperative accuracy is currently insufficient to warrant changing the procedure, or the morbidity of intracavitary reoperation is too high to allow a delay in identifying the patient with positive nodes.

Sentinel Node Mapping and Extent of Colon Resection

Appropriate procedures for some colon cancers have been described for more than a century. These procedures are designed not only to clear the proximal and distal margins, but more importantly, to encompass the likely lymphatic drainage of the segment of bowel containing the cancer. As Dr. Lin and coauthors note, aberrant lymphatic drainage (in a small percentage of patients) can be detected using lymphatic mapping. This has allowed surgeons to include such nodes in the resection. If these nodes contain cancer, the patient presumably benefits from their removal. Should additional nodes be removed when aberrant drainage is noted?

Patients in whom the "highest" node is positive have a poor prognosis. If an aberrant sentinel node contains cancer, many surgeons would wish to remove the next echelon of nodes in an effort to remove all tumor. Currently, we do not know how to locate these nodes. How much bowel must be sacrificed in an effort to remove such nodes?