Relapses were identified by the sudden and marked increase in the number of hospital procedures (y axis), accompanied by a change in treatment associated with a relapse. Relapses were identified by the sudden and marked increase in the number of hospital procedures (y axis), accompanied by a change in treatment associated with a relapse. The RFS period (x axis) was determined from the moment of intervention up to the following relapse. As CAR-T and HCT are second line ‘salvage’ treatments, RFS is considered a plausible surrogate endpoint for overall survival. CAR-T, chimeric antigen receptor T-cell; HCT, haematopoietic cell transplant; RFS, relapse-free survival. Duane Schulthess et al. BMJ EBM doi:10.1136/bmjebm-2019-111226 ©2019 by BMJ Publishing Group Ltd