IL6 and neoplasm: Circulating level of IL-6 rises within 3 to 10 days after the transfusion of CAR-T cells and declines along with tumor regression 10 to 21 days post-infusion.[8,9] Serum level of IL-6 has been suggested to correlate with the severity of CRS in patients treated with CAR-T cells.[10,11] Blocking IL-6 signaling has been demonstrated to effectively mitigate clinical symptoms of CRS induced by CAR-T cell therapy.[12,13] In our patient, CRS developed on day 5, followed by a significant release of IL-6 on day 7 post-infusion.