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February 2022BACKGROUND
Cutaneous melanoma is an aggressive form of skin cancer with the potential to metastasize to distant sites. Detection of disease in regional lymph nodes is routinely used to stage melanoma, and sentinel lymph node biopsy (SLNB) is indicated for all patients with biopsy-proven thickness of melanoma greater than 1.0 mm.
Identification of sentinel lymph nodes (SLNs) in head and neck melanoma can be particularly challenging, due in part to the unpredictable and diffuse lymphatic drainage of the head and neck. The use of a combination of radioisotope (RI)—most commonly, technetium-99 m sulfur colloid—and blue dye (BD) is considered the gold standard for identifying SLNs in melanoma. However, in practice, variations remain, with some surgeons using BD alone or RI alone. Some of these decisions depend on available resources; RI is more costly and requires coordination with nuclear medicine colleagues for preoperative administration.
Recently, the introduction of indocyanine green (ICG), a near-infrared fluorescent dye that can be detected intraoperatively using a handheld probe, has further expanded the options available for identifying nodal metastases. ICG offers several potential advantages over BD, and has emerged as a supplement to or even replacement for BD or RI. ICG can be visualized transcutaneously up to 1 cm in depth, does not stain tissue (which has been reported for BD), and has a lower side effect/anaphylactic profile than BD. Unlike RI, ICG does not involve any radiation and does not require preoperative injection with nuclear medicine specialists. Blue dye, on the other hand, requires direct visualization but does not require additional equipment. To date, there are few head-to-head comparisons among ICG, BD, and RI in cutaneous head and neck melanoma (Table 1).
Table 1: Studies Conducted That Examine the Use of RI, BD, and ICG in Patients With Cutaneous Melanoma.
| Study | Design | Number of H&N Patients | False Negative Rate | Identification Rate |
|---|---|---|---|---|
| Fujisawa et al.2 | Prospective cohort | 4 | Not reported | ICG: 13/13 (100%) RI: 11/13 (84.6%) BD: 8/13 (61.5%) |
| Knackstedt et al.3 | Prospective cohort | 61 | ICG + RI: 9.1% | Not reported |
| Vahabzadeh-Hagh et al.4 | Prospective cohort | 14 | Not reported | ICG: 12/14 (86%) RI (n = 14): 86% BD (n = 5): 60% |
| Niebling et al.5 | Meta-analysis | Unknown (137 melanoma studies) | Not reported RI: 6.9% BD: 6.1% BD + RI: 3.4% ICG + RI: 0% | ICG: 100% RI: 100% BD: 89% BD + RI: 99% ICG + RI: 100% |
BEST PRACTICE
Our literature review suggests that ICG alone and RI alone are both superior to BD alone in identifying SLNs in head and neck cutaneous melanoma, and that a combination of RI + BD or RI + ICG is superior to any one modality alone. Preliminary data suggest that, when available, ICG may be appropriate to use as a substitute for BD in conjunction with RI to reduce false negatives. Prospective and randomized studies are needed to explore whether or not ICG can be used as a single modality to identify SLNs in cutaneous head and neck melanoma.