Sentinel lymph node (SLN) mapping has become a cornerstone of oncologic surgery because it is a proven method for identifying nodal disease in
melanoma and
breast cancer. In addition, it can ameliorate the surgical morbidity secondary to
lymphadenectomy. However, experience with SLN mapping for
carcinoma of the colon and other visceral
malignancies is limited. This study represents an update to our initial pilot experience with SLN mapping for
carcinoma of the colon. Consenting patients over the age of 18 diagnosed with
adenocarcinoma of the colon were included in this study. At the time of operation, 1 to 2 mL of
isosulfan blue was injected with a 25-gauge needle into the subserosa at 4 sites around the edge of the palpable
tumor. The SLN was identified visually and excised followed by a standard
lymphadenectomy and surgical resection. SLNs were evaluated by standard
hematoxylin and
eosin (H&E) evaluation as well as immunohistochemical (IHC) techniques for
carcinoembryonic antigen and
cytokeratin if the H&E was negative. Sixty-nine patients underwent SLN mapping. A SLN was identified in 93 per cent (64 of 69) of patients. Nodal
metastases were identified in 38 per cent (26 of 69) of patients overall. In 5 patients, the only positive node identified was the SLN, 2 of which were positive by IHC criteria alone. Therefore, 3 per cent (2 of 69) of patients were upstaged by SLN mapping. This technique was 100 per cent specific while being 46 per cent sensitive. Fourteen patients had false-negative SLNs.
Metastasis to regional lymph nodes remains the key prognostic factor for
colon cancer. SLN mapping is feasible for
colon cancer and can identify a subset of patients who could benefit from
adjuvant chemotherapy. Although SLN mapping did not alter the surgical management of
colon cancer, it does make possible a more focused and cost-effective pathologic evaluation of nodal disease. We do not suggest routine utilization of SLN mapping for
colon cancer, but we believe that the data supports proceeding with a national trial.