A feasibility study of indocyanine green fluorescence mapping for sentinel lymph node detection in cutaneous melanoma

Objectives: Sentinel lymph node biopsy (SLNB) is standard of care for staging regional LN in AJCC stage IB-IIC melanoma; using dual localization with radiolabelled colloid and blue dye. Combining these gives optimal accuracy; drawbacks include cumulative radiation exposure for healthcare workers, coordination between disciplines and anaphylaxis. An alternative tracer agent is indocyanine green (ICG); an optical enhancer that fluoresces in the near infrared range. This prospective cohort study assesses the feasibility of using ICG as a tracer agent to detect SLN in cutaneous melanoma. Methods: Primary melanoma patients diagnosed with pT1b-pT4b tumours undergoing SLNB were recruited over a 6-month period at a tertiary referral centre. All underwent standard preoperative lymphoscintigraphy (LSG) using 20-40MBq of Tc99radiolabelled nanocolloid plus intraoperative Patent Blue dye (PBD). ICG was administered as a third tracer agent intraoperatively. Results: 62 patients (33M/29F) were recruited; median age was 61 years. Median melanoma Breslow thickness was 1.6mm. 144 specimens containing 135 SLN were excised. Concordance rate for all 3 tracer agents was 88.1%(119/135 LN); that for radioisotope/PBD was 88.2%(95%CI:82.2,93.7). There were no discordance pairs between radioisotope/PBD compared to radioisotope/PBD/ICG. Radioisotope/ICG significantly increased the sensitivity of detecting SLN to 98.5%(95%CI:94.8,99.8); p<0.00001 compared to radioisotope/PBD. Concordance rate of intraoperative ICG drainage pattern with LSG was 22.6%. Conclusion: ICG utilization showed comparable sensitivity with gold standard. Technical challenges e.g. ICG leakage into biopsy field, poor concordance with LSG limits its efficacy in melanoma SLNB. We therefore do not recommend replacing current practice with ICG alone or by using a combination with TC99.