A retrospective study was conducted with a continuous cohort of patients with cutaneous melanoma who had undergone SLN biopsy with Technetium-99m-labeled Tilmanocept at the California Pacific Medical Center (San Francisco, CA) and Moffitt Cancer Center (Tampa, FL) between January 2008 and August 2014. No patients were excluded. Demographic information, tumor site, tumor characteristics and lymph node characteristics were collected. This study was approved by the institutional review boards at both participating centers that this was a retrospective review of the existing patient data in each institution with the IRB allowing -no additional oral or written consents from individual patients. The data from each institution was encrypted according to the HIPAA regulations and analyzed by a statistician in its encrypted format.
Technetium-99m-labeled Tilmanocept was used for SLN biopsy in a standardized manner. Patients received a fixed dose of 50 μg of [99mTc] Tilmanocept (∼2.7 nmol) with a varying amount of radioactivity. It was administered by intradermal injection to the area surrounding the primary cutaneous melanoma. Same day surgery patients received .6 mCi of 99 mTc, while next day surgery patients received 2.0 mCi (timing of injection was at the surgeon’s discretion). Preoperative lymphoscintigraphy was performed for each patient to identify the location of SLNs. Intraoperatively, a handheld gamma probe was used to locate the relevant SLNs. A SLN was defined as any node that exceeds the background count plus three times the standard deviation of the background (“3-sigma rule”)36 (link) or whose radioactivity exceeds 10% of the most radioactive node identified (“10% rule”).34 (link),37 (link) Blue dye injection was as the discretion of the surgeon. Comparison between blue dye and Technetium-99m-labeled Tilmanocept identification of SLN was discussed in a previously published study.23 (link) In this study, analysis was performed only in the Technetium-99m-labeled Tilmanocept-identified SLNs. Histological evaluation of SLNs has been published previously in detail.20 (link)Continuous variables were summarized with mean, median and range, and categorical variables using frequencies and percentages. Univariate analyses examining the relationship between tumor characteristics and SLN biopsy status were performed using t-tests, Chi-square tests and Fisher’s exact tests. A multivariate logistic regression model was developed to further assess characteristics independently associated with having a single vs multiple SLNs. All tumor characteristics (except Clark level) were included initially; variables that did not reach a significance of P < .1 were removed sequentially. All statistical analyses were conducted using STATA version 13 (StataCorp, College Station, TX).
Technetium-99m-labeled Tilmanocept was used for SLN biopsy in a standardized manner. Patients received a fixed dose of 50 μg of [99mTc] Tilmanocept (∼2.7 nmol) with a varying amount of radioactivity. It was administered by intradermal injection to the area surrounding the primary cutaneous melanoma. Same day surgery patients received .6 mCi of 99 mTc, while next day surgery patients received 2.0 mCi (timing of injection was at the surgeon’s discretion). Preoperative lymphoscintigraphy was performed for each patient to identify the location of SLNs. Intraoperatively, a handheld gamma probe was used to locate the relevant SLNs. A SLN was defined as any node that exceeds the background count plus three times the standard deviation of the background (“3-sigma rule”)36 (link) or whose radioactivity exceeds 10% of the most radioactive node identified (“10% rule”).34 (link),37 (link) Blue dye injection was as the discretion of the surgeon. Comparison between blue dye and Technetium-99m-labeled Tilmanocept identification of SLN was discussed in a previously published study.23 (link) In this study, analysis was performed only in the Technetium-99m-labeled Tilmanocept-identified SLNs. Histological evaluation of SLNs has been published previously in detail.20 (link)Continuous variables were summarized with mean, median and range, and categorical variables using frequencies and percentages. Univariate analyses examining the relationship between tumor characteristics and SLN biopsy status were performed using t-tests, Chi-square tests and Fisher’s exact tests. A multivariate logistic regression model was developed to further assess characteristics independently associated with having a single vs multiple SLNs. All tumor characteristics (except Clark level) were included initially; variables that did not reach a significance of P < .1 were removed sequentially. All statistical analyses were conducted using STATA version 13 (StataCorp, College Station, TX).
