Ex vivo indocyanine green fluorescence imaging for the detection of lymph node involvement in advanced‐stage ovarian cancer

Background and objectives The aim of this study was to evaluate the role of indocyanine green (ICG) fluorescence imaging (FI) for the ex vivo detection of metastatic lymph nodes (LNs) in advanced stage ovarian cancer (AOC). Methods Paraffin‐embedded LNs from patients included in a previous ICG‐FI study (Protocol NCT01834469) were further assessed for fluorescence. Intravenous injection of ICG was delivered intraoperatively. Tumor‐to‐background ratios (TBRs) were calculated. Results A total of 675 LNs from 19 patients were analyzed. The mean LN number per patient was 29.3 (median: 24; range 2‐77). Seventy‐three LNs were malignant (10.8%), 602 were benign (89.2%). The mean TBR of all LNs was 1.5 (SD 0.8). With a cut‐off TBR of 1.3, the sensitivity, specificity, positive predictive, and negative predictive values of ICG‐FI for retroperitoneal LNs were 80%, 41%, 2.8%, and 99%, respectively. On univariate analysis, only the fluorescence ratio (TBR ≥ 1.3) was correlated with malignancy at pathology ( P = 0.03). No predictive factors of pathological LN status were found on multivariate analysis. Conclusions Ex vivo ICG‐FI of retroperitoneal LNs in AOC had good sensitivity but poor specificity. However, its high negative predictive value could make it an appropriate complementary tool to focus pathological analysis on fluorescent LNs.