Identification of Patients with Intermediate Thickness Melanoma at Low Risk for Sentinel Lymph Node Positivity

Abstract

Introduction Sentinel lymph node (SLN) biopsy is recommended for all patients with intermediate thickness melanomas. We sought to identify such patients at low risk of SLN positivity. Methods All patients with intermediate thickness melanomas (1.01–4 mm) undergoing SLN biopsy at a single institution from 1995–2011 were included in this retrospective cohort study. Univariate and multivariate logistic regression determined factors associated with a low risk of SLN positivity. Classification and regression tree (CART) analysis was used to stratify groups based on risk of positivity. Results Of the 952 study patients, 157 (16.5%) had a positive SLN. In the multivariate analysis, thickness <1.5 mm (OR= 0.29), age ≥60 (OR=0.69), present tumor infiltrating lymphocytes (TIL) (OR=0.60), absent lymphovascular invasion (LVI) (OR=0.46), and absent satellitosis (OR=0.44) were significantly associated with a low risk of SLN positivity. CART analysis identified thickness of 1.5 mm as being the primary cut point for risk of SLN metastasis. Patients with a thickness of <1.5 mm represented 36% of the total cohort and had a SLN positivity rate of 6.6% (95% CI=3.8–9.4%). In patients with melanomas <1.5 mm in thickness, the presence of additional low risk factors identified 257 patients (75% of patients with <1.5 mm melanomas) in which the rate of SLN positivity was <5%. Discussion Despite a SLN positivity rate of 16.5% overall, substantial heterogeneity of risk exists among patients with intermediate thickness melanoma. Most patients with melanoma between 1.01–1.5 mm have a risk of SLN positivity similar to that in patients with thin melanomas.

Stratifying SLN incidence in intermediate thickness melanoma patients

“…We were only able to find a small group of patients who fall into that less than 5% risk category such as demonstrated by the work by Bartlett et al 13 We found a number of subgroups with rates of positive SLNB less than 10%, however, only patients <60, with a Breslow thickness of 1.50–1.99, located on the head/neck/upper extremity and without any high-risk features had a positive SLNB rate of less than 5%, representing 1.9% of our study population (n = 65). 27.6% of patients (n = 936) had rates <10%: all low risk patients had a Breslow thickness of 1.01–1.99 mm.…”

“…However, overall we were unable to reproduce the low risk groups of positive SLNB as reported by Bartlett et al, and we did not find tumor infiltrating lymphocytes and absent tumor regression to be protective in our analysis. 13,26 …”

“…9–12 Prior studies have reported SLNB+ rates of around 15–25% in intermediate thickness melanoma. 2,13–15 Overall, sentinel lymph node biopsy has been associated with low morbidity compared to elective lymphadenectomy. 16,17 …”

“…18 Recently published work by Bartlett et al has identified subgroups of patients (absent LVI, absent mitoses, and either absent regression or age of 60 and older) with intermediate thickness melanoma who may be at similarly low risk (<5%) for a positive sentinel lymph node biopsy as thin melanoma groups. 13 Particularly in the older population of patients, the question arises as to who may be spared a SLNB. Similarly, prior papers have found the presence or absence of high-risk histopathologic features such as ulceration and lymphovascular invasion to be predictors of a positive sentinel lymph node biopsy.…”

Sentinel lymph node biopsy for ocular adnexal melanoma

“…The majority of reports from institutions other than ours to date on SLNB for ocular adnexal melanoma included one to four patients (Wilson et al 2001;Vuthaluru et al 2013;Wainstein et al 2014). (Morton et al 2014;Bartlett et al 2016). (Cohen et al 2013) In that report, both of the conjunctival melanomas associated with positive SLNs were in non-bulbar locations.…”