We examined baseline (prelymphodepletion) NfL levels in 30 individuals (median [range] age, 64 [22-80] years; 12 women [40%] and 18 men [60%]; 23 [77%] with a history of diffuse large B-cell lymphoma) treated with CD19 CAR T cells (63% axicabtagene ciloleucel; Table 1). The gene discussed is NEFL; the disease is diffuse large B-cell lymphoma.