Comparison of sentinel lymph node micrometastatic tumor burden measurements in melanoma.
BACKGROUND
Multiple methods have been proposed to classify the micrometastatic tumor burden in sentinel lymph nodes (SLN) for melanoma. The purpose of this study was to determine the classification scheme that best predicts nonsentinel node (NSN) metastasis, disease-free survival (DFS), and overall survival (OS).


METHODS
A single reviewer reanalyzed tumor-positive SLN from a multicenter, prospective clinical trial of patients with melanoma ≥ 1.0 mm Breslow thickness who underwent SLN biopsy. The following micrometastatic disease burden measurements were recorded: Starz classification, Dewar classification (microanatomic location), maximum diameter of the largest focus of metastasis, maximum tumor area, and sum of all diameters. Univariate and multivariate models and Kaplan-Meier analysis were used to evaluate each classification system.


RESULTS
We reviewed 204 tumor-positive SLNs from 157 patients. On univariate analysis, all criteria except Starz classification were statistically significant risk factors for NSN metastasis. On multivariate analysis, including Breslow thickness, ulceration, age, sex, and NSN status, maximum diameter (using a cut-off of 3 mm) was the only classification system that was an independent risk factor predicting DFS (hazard ratio 2.31, p = 0.0181) and OS (hazard ratio 3.53, p = 0.0005). By Kaplan-Meier analysis, DFS and OS were significantly different among groups using maximum diameter cut-offs of 1 and 3 mm.


CONCLUSIONS
Maximum tumor diameter outperformed other measurements of metastatic tumor burden, including microanatomic tumor location (Dewar classification), Starz classification, maximum tumor area, and sum of all diameters for prediction of survival. Maximum tumor diameter is a simple method of assessing micrometastatic tumor burden that should be reported routinely.
Hiram C Polk Jr MD Department of Surgery, University of Louisville, Louisville, KY.
Michael E
ME
Egger
Scott and White Hospital, Temple, TX.
Matthew R
MR
Bower
Hiram C Polk Jr MD Department of Surgery, University of Louisville, Louisville, KY.
Irene A
IA
Czyszczon
Hiram C Polk Jr MD Department of Surgery, University of Louisville, Louisville, KY.
Hanan
H
Farghaly
Intermountain Surgical Oncology, Murray, UT.
R Dirk
RD
Noyes
Department of Surgery, University of South Florida, Tampa, FL.
Douglas S
DS
Reintgen
Hiram C Polk Jr MD Department of Surgery, University of Louisville, Louisville, KY.
Robert C G
RC
Martin
Hiram C Polk Jr MD Department of Surgery, University of Louisville, Louisville, KY.
Charles R
CR
Scoggins
Department of Statistics, University of Kentucky, Lexington, KY.
Arnold J
AJ
Stromberg
Hiram C Polk Jr MD Department of Surgery, University of Louisville, Louisville, KY. Electronic address: mcmasters@louisville.edu.
Kelly M
KM
McMasters
D000328:Adult; D005260:Female; D006801:Humans; D016015:Logistic Models; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008545:Melanoma / Q000401:mortality / Q000473:pathology*; D008875:Middle Aged; D015999:Multivariate Analysis; D061206:Neoplasm Micrometastasis / Q000473:pathology*; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D021701:Sentinel Lymph Node Biopsy; D012878:Skin Neoplasms / Q000401:mortality / Q000473:pathology*; D016019:Survival Analysis; D047368:Tumor Burden