EFS of frontline treatment with RUX. (A) Kaplan-Meier estimated EFS in all patients who received RUX. (B) EFS in patients by treatment status at enrollment (precorticosteroid treated vs precorticosteroid untreated). No significant difference was detected between the 2 groups by the log-rank test (P = .634). For nonresponders, EFS was defined as the date of enrollment plus 1 day.