Comparison of Technetium-99m Tilmanocept to Technetium-99 Sulfur Colloid Radiotracer for Sentinel Lymph Node Biopsy in Head and Neck Melanoma

Background: Sentinel lymph node biopsy (SLNB) is integral to management of head and neck melanomas (HNM). Here, we evaluate how radiotracer selection (Tc-99m tilmanocept or Tc-99m sulfur colloid) and imaging modality (planar imaging or single positron emission computed tomography (SPECT)) may influence SLNB and its outcomes. Methods: We performed a retrospective chart review of patients who received SLNB for HNM at our institution between January 2000 and July 2022. Results: A total of 211 patients received Tc-99m tilmanocept (Tc-tilmanocept) and 113 received Tc-99m sulfur colloid (Tc-SC). There was no difference between Tc-tilmanocept and Tc-SC in terms of number of nodal levels to which the radiotracers localized (1.48 +/- 0.93 SD vs 1.38 +/- 0.93, respectively). Tc-tilmanocept had a lower rate of failed sentinel node identification as reported on radiology reports compared to Tc-SC (1.9% vs 11.5%, P < .001). There was a lower 5-year recurrence rate with Tc-tilmanocept versus Tc-SC (20.9% vs 28.3%, respectively P = .07), but this difference was not significant. When analyzing only cases in which SPECT was obtained, this there was no observed difference in 5-year recurrence rate. With SPECT, fewer patients had non-specific description of their node localization as "cervical" without further detailing of nodal basin (0% SPECT vs 9.7% non-SPECT, P < .001). Multivariable linear regression analysis for predictors of HNM 5-year recurrence found the odds ratio for SPECT imaging was 0.43, but not statistically significant (P = .06). Conclusions: Tc-tilmanocept may be associated with greater rate of successful radiotracer migration along lymphatics compared to Tc-SC. SPECT imaging may confer more precision of the nodal basin to which radiotracer localizes as fewer patients receiving SPECT had radiology findings showing nonspecific localization of nodes to "cervical" basins without further specification. More patients are necessary to determine if Tc-tilmanocept and SPECT imaging are associated with lower melanoma recurrence rate.