Detection of sentinel lymph nodes in patients with endometrial cancer undergoing robotic-assisted staging: A comparison of colorimetric and fluorescence imaging

Objective To retrospectively compare results from lymphatic mapping of pelvic sentinel lymph nodes (SLN) using fluorescence near-infrared (NIR) imaging of indocyanine green (ICG) and colorimetric imaging of isosulfan blue (ISB) dyes in women with endometrial cancer (EC) undergoing robotic-assisted lymphadenectomy (RAL). A secondary aim was to investigate the ability of SLN biopsies to increase the detection of metastatic disease. Methods Thirty-five patients underwent RAL with hysterectomy. One mL ISB was injected submucosally in four quadrants of the cervix, followed by 0.5 mL ICG [1.25 mg/mL] immediately prior to placement of a uterine manipulator. Retroperitoneal spaces were dissected for colorimetric detection of lymphatic pathways. The da Vinci® camera was switched to fluorescence imaging and results recorded. SLN were removed for permanent analysis with ultra-sectioning, H&E, and IHC staining. Hysterectomy with RAL was completed. Results Twenty-seven (77%) and 34 (97%) of patients had bilateral pelvic or aortic SLN detected by colorimetric and fluorescence, respectively (p=0.03). Considering each hemi-pelvis separately, 15/70 (21.4%) had "weak" uptake of ISB in SLN confirmed positive with fluorescence imaging. Using both methods, bilateral detection was 100%. Ten (28.6%) patients had lymph node (LN) metastasis, and 9 of these had SLN metastasis (90% sensitivity, one false negative SLN biopsy). Seven of nine (78%) SLN metastases were ISB positive and 100% were ICG positive. Twenty-five had normal LN, all with negative SLN biopsies (100% specificity). Four (40%) with LN metastasis were detected only by IHC and ultra-sectioning of SLN. Conclusions Fluorescence imaging with ICG detected bilateral SLN and SLN metastasis more often than ISB, and the combination resulted in 100% bilateral detection of SLN. Ultra-sectioning/IHC of SLN increased the detection of lymph node metastasis.