Prolonged detection of GD2–T cells within the peripheral blood of patients was highly concordant with the percentage of helper (CD4⁺ cells) and central memory cells (CD45RO⁺CD62L⁺) in the infused product. Using regression analysis, it was determined that each 1-unit increase in the number of CD4⁺ cells within the infused product was associated with a 2.28 increase in the log (duration) of CAR-CTL (A) and a 9.83 increase in the log (duration) of CAR-ATC (B). Further, each 1-unit increase in the percentage of central memory cells was associated with a 6.1 increase in the log (duration) of CAR-CTL (C) and a 6.63 increase in the log (duration) of CAR-ATC (D) in the T-cell product.