Sentinel lymphadenectomy in vulvar cancer using near-infrared fluorescence from indocyanine green compared with technetium 99m nanocolloid

Abstract

Objective: Nowadays, sentinel diagnostic is performed using technetium 99m (99mTc) nanocolloid as a radioactive marker and sometimes patent blue. In the last years, indocyanine green has been evaluated for sentinel diagnostic in different tumor entities. Indocyanine green is a fluorescent molecule that emits a light signal in the near-infrared band after excitation. Our study aimed to evaluate indocyanine green compared with the criterion-standard 99mTc-nanocolloid. Methods: We included patients with primary, unifocal vulvar cancer of less than 4 cm with clinically node-negative groins in this prospective trial. Sentinel diagnostic was carried out using 99mTc-nanocolloid, indocyanine green, and patent blue. We examined each groin for light signals from the near-infrared band, for radioactivity, and for blue staining. A sentinel lymph node was defined as a 99mTc-nanocolloid-positive lymph node. All sentinel lymph nodes and all additional blue or fluorescent lymph nodes were excised and tested and then sent for histologic examination. Results: In all, 27 patients were included in whom we found 91 sentinel lymph nodes in 52 groins. All these lymph nodes were positive for indocyanine green, also giving a sensitivity of 100% (95% confidence interval [CI], 96.0%-100%) compared with 99mTc-nanocolloid. Eight additional lymph nodes showed indocyanine green fluorescence but no 99mTc positivity, so that the positive predictive value was 91.9%(95% confidence interval, 84.6%-96.5%). In 1 patient, a false-negative sentinel missed by all 3 modalities was found. Conclusions: Our results show that indocyanine green is a promising approach for inguinal sentinel identification in vulvar cancer with a similar sensitivity as radioactive 99mTc-nanocolloid and worth to be evaluated in further studies.