Combining radioisotopic and blue-dye technique does not improve the false-negative rate in sentinel lymph node mapping for colorectal cancer.

Purpose: This study was designed to assess the feasibility of a combined colorimetric and radioisotopic technique in the detection of the sentinel lymph node in colorectal cancer.

Methods: This prospective dual-center study included 64 patients. Using endoscopy on D0, a radiolabeled colloid was injected into the peritumoral submucosa, followed by a lymphoscintigraphy. Intraoperatively, on D1, lymphatic mapping was performed by using a visual method and radioguided detection after subserosal peritumoral injection of patent blue. Twenty-nine patients were injected only with the patent blue, 18 patients only with the radioactive tracer, and the other 17 patients benefited from both techniques.

Results: The detection rate was 92 percent. The average number of sentinel nodes harvested was 2.8. Twenty-four of 59 patients were pN+ (40 percent) and in 12 cases the sentinel lymph node was histologically negative, although there was a positive nonsentinel node (false-negative rate, 50 percent). The false-negative rate for the combined, radioisotopic, and colorimetric techniques were 63, 60, and 36 percent, respectively. In four patients, the sentinel node was the only metastatic site (4/24, 17 percent), and in two of these four patients, the sentinel lymph node presented with micrometastases (<2 mm). The radioisotopic technique allowed us to highlight a lateral drainage of two rectal cancers (2/13, 15 percent). The concordance between the blue and radioactive sentinel nodes was 43 percent.

Conclusions: The addition of a radioisotopic method using submucosal injection does not improve the false-negative rate. The sentinel lymph node technique in colorectal cancer is feasible, although the false-negative rate is such that the technique should still be considered as experimental.