Kaplan-Meier curves of EFS according to MNC. Six-year EFS estimates: 80% for MNC 51-54, 89% for MNC 54-57, 99% for MNC 58-66. HR MNC 58-66 vs MNC 51-54: 0.49; HR (MNC 54-57 vs MNC 51-54): 0.04 Wald test of heterogeneity: P = .0025. Considered as 3-ordered categorical variable (MNC 58-66 vs MNC 54-57 vs MNC 51-54), the estimated HR was 0.36 (95% CI, 0.22 to 0.58); Wald test for linear trend: P < .0001.