TFx and TFx fold change levels over time. (A) TFx levels observed during CAR-T treatment categorized by response status. (B) TFx fold change observed relative to baseline categorized by response status. For week 1 and onward samples with undetectable ctDNA, LOD95 was substituted for TFx to reflect a minimum fold change in TFx. (C) TFx with corresponding LOD95 for 2 example patients after CAR-T achieving CR at 1 month and maintaining response through 1 year (green box; left) and 2 patients achieving PR at 1 month and subsequently converting to CR (blue box; right). Of note, LOD95 reflects the lowest TFx at which there is 95% likelihood of detection, as opposed to the lowest detectable TFx. (D) TFx with corresponding LOD95 for 2 example patients after CAR-T with PD at 1 month (orange box, left) and 2 example patients achieving CR or PR at 1 month and subsequently progressing (purple box; right). For panels C-D, blue line indicates TFx. (E) Overall performance of predicting patient response status at week 1 and week 2 using TFx fold change from baseline. ROC, Receiver Operating Characteristic.