Sentinel lymph node mapping in colon cancer using radiocolloid as a single tracer: a feasibility study.

Objective: Evaluation of the feasibility and safety of radiocolloid as a tracer for sentinel lymph node (SLN) mapping in colon cancer.

Methods: A feasibility study was conducted in consecutive colon cancer patients who were surgically treated at our institute. During preoperative colonoscopy, radiocolloid was injected around the tumour, followed by scintigraphic imaging to identify SLNs. SLNs were identified intraoperatively by a gamma probe and postoperatively by additional ex-vivo scintigraphy of the resection specimen. All retrieved SLNs were examined by histopathological ultrastaging. Standard oncologic laparoscopic resections with lymphadenectomy were performed following the identification of SLNs in all patients.

Results: Fourteen patients were included. At least one SLN was identified in 86% of patients. In one patient (7%) SLNs could be detected intraoperatively. In 83% of patients, the SLNs accurately reflected the tumour status of the remaining lymph nodes. Aberrant lymphatic drainage was preoperatively identified in one patient (7%), but this could not be confirmed intraoperatively. Sensitivity was 67% and the false-negative rate was 33%. Seventeen per cent of patients were upstaged because of SLN micrometastases.

Conclusion: SLN mapping in colon cancer using radiocolloid as a single tracer is feasible and safe. However, it was difficult to identify SLNs intraoperatively because of high radioactivity at the injection site. Furthermore, the protocol is labour intensive, especially because of the additional colonoscopic tracer injection. Sensitivity is not better than when blue dye is used, and aberrant lymphatic drainage patterns are scarce. Therefore, this technique is not preferred for SLN mapping in colon cancer.