Accuracy of ICG compared with technetium-99 m for sentinel lymph node biopsy in vulvar cancer

Abstract

Purpose: Sentinel lymph node biopsy with radioactive tracer is the standard-of-care in lymph node status assessment in vulvar cancer. Indocyanine green fluorescence-ICG is a promising detection method, due to its advantages over technetium-99 m. In vulvar cancer, the procedure is controversial due to study heterogeneity and the small sample size in previous studies. This study evaluates ICG sentinel lymph node detection compared with the criterion-standard with technetium (dual modality method).

Methods: Preoperative technetium and intraoperative ICG for sentinel lymph node have been prospectively evaluated in early-stage vulvar cancer. The primary endpoint was to determine accuracy in the detection rate for ICG compared with technetium. Secondary objectives included tracer modality relationship with obesity, tumor size and location.

Results: In total, 75 patients participated at 8 centers; 38 had lateral and 37 had midline vulvar tumors. The overall sentinel lymph node detection rate was 85.3 % for technetium and 82.7 % for ICG. For lateral tumors, the detection rate was 84.2 % vs. 89.5 %, while it was 86.5 % vs. 75.7 % for middle tumors, using technetium and ICG, respectively. The median sentinel node harvest was 1.7 (range 1-4), with 24 % metastatic involvement. The sensitivity and positive predictive value for ICG based on the standard technique with technetium was 91.08 % (95 % CI, 83.76-95.84) and 94.8 % (95 % CI, 84.84-96.48), respectively. No significant differences were found comparing the two tracers in patients with midline lesions, obesity (body mass index ≥ 30) and tumor size ≥ 2-4 cm.

Conclusion(s): ICG shows comparable performance parameters to the gold-standard of radioisotope localization.

Keywords: ICG; Sentinel lymph node biopsy; Technetium; Vulvar cancer.