Predictors of nonsentinel lymph node positivity in patients with a positive sentinel node for melanoma.

BACKGROUND: Patients found to harbor melanoma micrometastases in the sentinel lymph node (SLN) are recommended to proceed to complete lymph node dissection (CLND), although the majority of patients will have no additional disease identified in the nonsentinel lymph nodes (NSLNs). We sought to assess predictive factors associated with finding positive NSLNs, and identify a subset of patients with low likelihood of finding additional disease on CLND.

STUDY DESIGN: We queried our prospective melanoma database for patients from January 1996 to August 2003 with a positive SLN. Univariable logistic regression models were fit for multiple factors and a positive NSLN. To derive a probabilistic model for occurrence of one or more positive NSLN(s), a multivariable logistic model was fit using a stepwise variable selection method.

RESULTS: Of 980 patients who underwent SLN biopsy for cutaneous melanoma, 232 (24%) had a positive SLN; 221 (23%) followed by CLND. Of these patients, 34 (15%) had one or more positive NSLN(s). In multivariable analysis, male gender (odds ratio [OR] 3.6 [95% CI 1.33, 9.71]; p = 0.01), Breslow thickness (OR 4.58 [95% CI 1.28, 16.36]; p = 0.019), extranodal extension (OR 3.2 [95% CI 1.0, 10.5]; p = 0.05), and three or more positive sentinel nodes (OR 65.81 [95% CI 5.2, 825.7]; p = 0.001) were all associated with the likelihood of finding additional positive nodes on CLND. Of 47 patients with minimal tumor burden in the SLN, only 1 (2%) had additional disease in the NSLN.

CONCLUSIONS: These results provide additional data to plan clinical trials to answer the question of who can safely avoid CLND after a positive SLN. Patients with minimal tumor burden in the SLN might be the most likely group, although defining "minimal tumor burden" must be standardized. Serial sectioning and immunohistochemistry on the NSLN in any "low-risk" group must be performed in a clinical trial to confirm that residual disease is unlikely before avoiding CLND can be recommended.