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.