A. Hanna1, A. J. Sinnamon1, R. Roses1, R. Kelz1, D. Elder1, X. Xu1, B. Pockaj2, D. Fraker1, G. Karakousis1 1University Of Pennsylvania,Philadelphia, PA, USA 2Mayo Clinic,Phoenix, AZ, USA
Introduction:
Sentinel lymph node (SLN) biopsy is routinely recommended for patients with intermediate (1.01 – 4.00 mm) thickness melanoma. Prior institutional data from our group,however, suggested significant variation in the risk for SLN metastasis for these patients and we therefore sought to identify subgroups within this cohort with low risk for SLN positivity using a large national data set.
Methods:
Patients with intermediate thickness melanomas who underwent SLN biopsy from 2010 to 2013 were identified using the National Cancer Database. Clinical and pathologic variables associated with SLN positivity were analyzed using logistic regression. Classification and Regression Tree (CART) analysis was used to risk-stratify patients for SLN positivity.
Results:
Of the 23,440 study patients with intermediate thickness melanoma, 14.7% (95% CI, 14.2% – 15.1%) were found to have a positive SLN. Most (59.9%) patients were male and the median age was 62 years (IQR, 51 – 72 years old). In multivariate logistic regression, increased age (OR = 0.89/10 years, 95% CI 0.88 – 0.90), female gender (OR = 0.85, 95% CI 0.79 – 0.93), absence of lymphovascular invasion (LVI) (OR = 0.31, 95% CI 0.27 – 0.36), absent mitoses (OR = 0.61, 95% CI 0.54 – 0.70), a H&N, upper extremity, or shoulder primary site (OR = 0.55, 95% CI 0.49 – 0.63), decreased thickness (OR = 1.55/mm, 95% CI 1.48 – 1.63), and absent ulceration (OR = 0.74, 95% CI 0.68 – 0.81) all were significantly associated with having a negative SLN. In CART analysis, absent LVI, thickness < 1.7 mm, age < 56, and primary site were significant branch points (Figure 1). In patients 56 years of age or older with absent LVI and intermediate thickness lesions < 1.7 mm (29% of all patients analyzed), the rate of SLN positivity was < 5%.
Conclusion:
Despite a SLN positivity rate of 14.7% overall, there exists significant heterogeneity in the risk for SLN metastasis in patients with intermediate thickness melanoma. In a sizable group of patients (nearly 30% undergoing the procedure), the risk for SLN metastasis approximates that seen in lower risk thin melanomas, where the procedure is offered selectively. For these patients (56 years or older with lower depth intermediate lesions and absent LVI) careful consideration should be made weighing the risks and benefits of the SLN procedure.
