Sentinel lymph node biopsy is prognostic but not therapeutic for thick melanoma

Abstract

Sentinel lymph node biopsy (SNB) as a staging and therapeutic procedure in melanomas 1-4mm in thickness has been investigated extensively, however, the clinical value of SNB in thick melanomas is poorly understood. Patients undergoing operation for clinically node-negative melanoma >4mm in depth between 2003 and 2010 were identified in the Surveillance Epidemiology and End Results registry. Two groups were constructed: one with a wide excision with SNB and the other with wide excision alone. A total of 4,571 patients with clinically node-negative, thick melanoma were identified. The median age was 71years, 96.9% were white, and 64.3% were male. SNB was performed in 2,746 (60.1%) and was positive in 32.2%. Univariate analysis demonstrated SNB was associated with younger age (64 vs 75years; P<.001) and extremity primaries (P<.0001). On logistic regression, advanced age (P<.001), female sex (P=.009), and location in the head and neck region (P<.001) were associated with observation. On log-rank analysis, improved 5-year disease-specific survival (DSS) was associated with SNB (65 vs 62%; P=.008), location in the extremity versus head and neck or trunk (67 vs 61.5 and 60.3%; P=.004), female sex (69 vs 61%; P<.001), and no ulceration (74 vs 54%; P<.001). On Cox regression analysis, advanced age (P<.001), male sex (P=.01), trunk location (P=.0001), and ulceration (P<.001) continued to be associated with DSS. SNB was not associated with survival (P=.20). SNB status was a robust predictor of survival; a negative SNB had a 5-year DSS of 75.3 versus 44.1% (P<.0001), with a positive node. For patients with clinically node-negative, thick melanoma, SNB is a staging but not therapeutic procedure.