Sentinel lymph node mapping with fluorescent and radioactive tracers in vulvar cancer patients

Application of radioactive tracers for sentinel lymph node biopsy (SLNB) in vulvar cancer has been established, however, the use of radioisotopes is expensive and requires complex logistics. This exploratory study evaluated the feasibility of near-infrared fluorescence-based SLNB in comparison to the gold standard using radioactive guidance.

At Evangelische Kliniken Essen-Mitte (Essen, Germany) between 02/2015 and 04/2019, 33 patients with squamous cell vulvar cancer and unifocal tumors (32 midline, 1 lateral) smaller than 4 cm underwent SLNB as part of their routine primary surgical therapy. Radiolabeled nanocolloid technetium 99 (^99mTc) was injected preoperatively and indocyanine green (ICG) intraoperatively. Demographic and clinical data were retrieved from patients' records, and descriptive statistics were applied. The detection rate of the ICG fluorescence technique was compared with the standard radioactive approach.

In patients with midline tumors, bilateral SLNB was attempted. SLNB was feasible in 61/64 (95.3%) groins with ^99mTc and in 56/64 (87.5%) with ICG. In total, 125 SLNs were excised; all SLNs were radioactive and 117 (93.6%) also fluorescent. In 8 patients with BMI > 30 kg/m², SLNB was successful in 14/15 groins (93.3%) with ^99mTc and 13/15 groins (86.7%) with ICG. Upon final histology, infiltrated nodes were present in 9/64 (14.1%) groins and 10/125 SLNs; one positive SLN was not detected with ICG.

SLNB using ICG is a promising technique, however, the detection rate obtained was slightly lower than with ^99mTc. The detection rate increased over time indicating that experience and training may play an important role besides further methodological refinements.