Assessment of a new scoring system for predicting non-sentinel node positivity in sentinel node-positive melanoma patients.

BACKGROUND: When completion lymph node dissection (CLND) is performed in sentinel node (SN)-positive melanoma patients, a positive non-sentinel node (NSN) is found in approximately 20% of them. Recently, Murali et al. proposed a new scoring system (non-sentinel node risk score, N-SNORE) to predict the risk of NSN positivity in SN-positive patients. The objectives of the current study were to identify factors predicting NSN positivity and to assess the validity of the N-SNORE in an independent patient cohort.
METHODS: All SN-positive patients who underwent CLND at a single institution between 1995 and 2010 were analyzed. Characteristics of the patient, primary melanoma, and SN(s) were tested for association with NSN positivity. Missing values were reconstructed using multiple imputation to enable multivariable analysis.
RESULTS: CLND revealed positive NSNs in 30 (23%) of 130 SN-positive patients. Primary melanoma regression (p = 0.03) was independently associated with NSN positivity. After adjustment because of missing data on perinodal lymphatic invasion, N-SNORE proved to be a significant stratification model in our patient cohort (p = 0.003): 5.9% NSN positivity in the very low risk category and 75.0% NSN positivity in the very high risk category.
CONCLUSIONS: Presence of regression in the primary melanoma was independently associated with a higher risk of NSN positivity. The slightly modified N-SNORE scoring system provided useful stratification of the risk for NSN positivity. However, lack of perinodal lymphatic invasion data may have reduced its predictive value.