Disease assessments will be performed at screening, after bridging, 1, 3, 6, 9 and 12 months after tisagenlecleucel infusion, and every 6 months in the second year, and annually up to 60 months after infusion. Efficacy will be assessed until progression; safety will be assessed throughout the study. A long term follow-up up to 15 years after CTL019 infusion will continue under a separate protocol (CCTL019A2205B)(NCT02445222).