Meta-analysis of sentinel lymph node positivity in thin melanoma (≤ 1mm)

Abstract

20032 Background: Indications for sentinel lymph node (SLN) biopsy in patients with thin (≤1mm) primary melanoma are as yet undefined, with selection criteria varying among institutions. We performed a meta-analyses of published studies to estimate the risk of regional nodal disease in this group of patients. Methods: MEDLINE (January 1966 to July 2007), EMBASE (January 1980 to July 2007), and Cochrane databases were searched for published studies or abstracts which reported on the rate of SLN positivity in patients with thin melanomas. Searches were supplemented by scanning bibliographies of included articles. Two authors independently extracted data. Study quality was assessed using the MINORS criteria. A meta-analysis was performed using fixed and random effect models. Results: 3,651 patients enrolled in 34 studies met inclusion criteria. Meta-analysis resulted in a random effects pooled SLN positivity rate of 5.6%. Significant heterogeneity among studies was detected (p=0.005, test of non-combinability), suggesting high variation among study outcomes. There was no statistical evidence of publication bias (p=0.21, Begg-Mazumdar test). 18 studies had a primary focus on SLN biopsy in melanomas ≤1mm. These studies reported select clinical and histopathologic data limited only to SLN positive patients (n=113). Among the tumors from these patients 6/98 (6.1%) were ulcerated, 17/54 (31.5%) showed regression, and 48/101 (47.5%) were invasive to Clark’s level IV/V. Only 3 patients for whom recurrence and survival data were available died of melanoma at follow-up. Conclusions: These data indicate that nodal involvement, as detected by the highly sensitive SLN technique, is rare in melanomas ≤ 1mm in thickness. In addition, the lack of complete clinicopathologic data from SLN biopsy negative patients in most of the published literature precludes the identification of reliable criteria to select patients who might benefit from SLN biopsy. Therefore, the benefits of SLN biopsy among patients with melanomas ≤ 1mm in thickness appear marginal. Given the increasing diagnosis of thin melanomas as well as the cost and morbidity associated with this procedure, alternative strategies to identify patients at risk for nodal disease, including molecular prognostic factors, are critically needed. No significant financial relationships to disclose.