Preliminary study on radioguided sentinel node identification in colon cancer.

The purpose of this study was to prove the prognostic value of the sentinel node (SN) in colon tumors, and to validate radioguided surgery in identifying the SN. Nodal metastases are a strong prognostic factor in patients operated on for colon or rectal cancer, decreasing the 5-year survival rate by approximately 20 per cent and dropping it to 30 per cent. Unfortunately, of 50 per cent of patients judged to be nodal disease-free at surgery, about 20 to 30 per cent will die from a local tumor relapse or distant metastases within 5 years of diagnosis. These data suggest that other steps are needed for more precise staging of patients, and specifically, to accurately harvest and study the nodes on which to base the prognosis. Mapping lymph nodes predictive of the whole basin status, referred to as SN, may help focus the pathologist's attention on a small but representative target, and achieve correct nodal harvesting, which includes atypical drainage pathways, when present. Twenty selected patients with colon tumor were administered a subserosal, peritumoral, intraoperative injection of blue dye and 99mTc-marked colloidal particles. The SN was identified visually and with a handheld gamma probe and was subsequently stitch-labeled. The operation was then conducted after standard surgical procedures, and the required lymphadenectomy was performed. Later, the probe was used to confirm radioactivity in the excised specimen and the absence of radioactivity in the operative field after resection; the purpose of the latter was to exclude the presence of aberrant routes of lymphatic drainage. The labeled SN were stained with hematoxylin and eosin and, in case of negative findings, cytokeratin immunostaining was performed. The remaining resected nodes were stained with hematoxylin and eosin. The probe identification of SN was 95 per cent overall (19/20); in 13 patients, a single SN was labeled, and two were labeled in six patients, harvesting 25 SN. In the 19 patients in whom a radioemitting SN was labeled, we recorded only one false-negative; in one case, a micrometastasis in the SN was the only extracolonic site. The blue dye identified the SN in 14 cases; in some of them, the number of nodes was overestimated (five single, seven double, and two triple SN) in comparison with the radioisotope, but at least one of the dyed nodes was also radioemitting. SN identification in colon cancers is a safe, fast, and easy procedure for ultrastaging the nodal basin. The technique involves a relatively flat learning curve and could become standard care for identifying the presence of nodal micrometastases at a low cost, thereby also making it affordable at small health centers.