Lymph Node Ratio Provides Prognostic Information in Addition to American Joint Committee on Cancer N Stage in Patients With Melanoma, Even If Quality of Surgery Is Standardized

Abstract

To investigate whether lymph node ratio (LNR) gives additional prognostic information to American Joint Committee on Cancer (AJCC) N stage in a melanoma treatment center where regional lymph node dissection (RLND) techniques are standardized. Lymph node ratio is the ratio of involved lymph nodes to total number of lymph nodes removed at RLND. It is a predictor of survival for melanoma patients. One possible explanation of this is variation in surgical quality. Regional lymph node dissection procedures performed between 1993 and 2006 were identified from a prospective melanoma database. Patients having axilla, groin, and neck (≥ 4 levels) RLNDs were allocated to both AJCC N stage groupings and LNR groupings using thresholds A 10% and less, B more than 10% to 25%, and C more than 25%. Lymph nodes retrieval for surgeons was equivalent or exceeded existing standards. For all RLNDs combined (n = 1514) and for the separate regions N1 and LNR A, N2 and LNR B, and N3 and LNR C all had similar numbers of patients allocated to each group with similar survival. The significant factors on multivariate analysis were LNR, primary melanoma Breslow thickness (but only when assessing AJCC stage T0-T3 vs T4), ulceration, AJCC N stage, age less than 50 years/50 years and more, and lymph node basin (groin better than axilla and neck). Lymph node ratio also allowed substaging of AJCC stage N3 patients. Standardized techniques for RLNDs result in LNR and AJCC N stage having similar percentages of cases in each grouping with similar survival. However, LNR is still an independent predictor in prognosis in these melanoma patients. Substaging may account for some of these observations.