M. G. Peters1, E. K. Bartlett1, R. E. Roses1, B. J. Czerniecki1, D. L. Fraker1, R. R. Kelz1, G. C. Karakousis1 1Hospital Of The University Of Pennsylvania,General Surgery,Philadelphia, PA, USA
Introduction: Patients with intermediate thickness cutaneous melanoma are routinely recommended for sentinel lymph node biopsy (SLNB) as standard of practice. Conversely, those with thin melanoma are selectively offered the procedure given the low risk of SLN positivity in this group overall. We sought to identify a low-risk subset of patients with intermediate thickness melanoma who, like many patients with thin melanoma, may be spared the additional LN procedure.
Methods: Demographics and histo-pathological characteristics of the primary tumor were reviewed for 952 patients undergoing SLNB for primary intermediate thickness cutaneous melanoma (1.01-4.00mm) treated at our institution from 1995-2011. Univariate analysis using chi-square and Wilcoxon rank-sum as appropriate was used to determine associations with SLN positivity. Factors approaching statistical significance (p<0.20) were included in a forward step-wise multivariate logistic regression. All significant factors (p<0.05) were then included in a risk scoring system.
Results: The rate of positive SLNB in the study cohort was 16.5% (n=157). In univariate analyses, significant factors associated with SLN positivity were increasing thickness (p<.001), absence of tumor infiltrating lymphocytes (p=.043), ulceration (p=.014), lymphovascular invasion (p<.001), and the presence of microsatellites (p<.001). With regards to age <60 (p=.18) and presence of mitoses (p=.071), there was a trend toward significant association with SLN positivity. When all of these factors were included in a multivariate model, five factors were identified as significantly associated with SLN positivity; younger age (<60 years, OR=1.52, p=.032), absence of tumor infiltrating lymphocytes (OR=1.64, p=.02), thicker primary tumors (OR=2.6 for 1.51-2, OR=3.5 for 2.01-4, p<.001), the presence of satellites (OR=2.2, p=.015), and lymphovascular invasion (OR=2.1, p=.014). These factors were used to develop a risk stratification scoring system (see Table). The rate of positive SLN ranged from 4.6% (when no factors were present, score=0) to 44.0% (when all factors were present, score= 5).
Conclusion:Patients with intermediate thickness melanoma can be risk stratified for SLN positivity using clinical and pathologic factors. While SLNB appears justified for the majority of patients with intermediate thickness melanomas, for appreciable minority (nearly 10%) the risk of LN positivity is more similar to that of low risk T1 (<1.0mm) melanomas. For this subgroup of patients, SLNB can be offered selectively.
