Baseline ⁸⁹Zr-Df-crefmirlimab (CD8 T-cell) uptake correlates with posttreatment tumor FDG-PET-CT response. (A-C) Representative baseline (BL) CD8 T-cell and paired FDG-PET imaging (and F/U scans ∼D50). (A) A 50-year-old female patient with stage II FL (at diagnosis): whole-body ⁸⁹Zr-Df-crefmirlimab scan 24 hours postinjection (p.i.) (left) at BL and day 51 on treatment with paired FDG-PET (right). Axial slices of left axillary mass demonstrate intense uptake at BL and CMR on treatment. RT fields are illustrated on the FDG-PET image. (B) A 86-year-old male with DLBCL: whole-body ⁸⁹Zr-Df-crefmirlimab scan 24 hours p.i. (left) at BL and F/U on treatment with paired FDG-PET (right). Axial slice of bilateral neck lesions demonstrate intense uptake at BL and CMR on treatment. RT fields are illustrated on the FDG-PET image. (C) A 76-year-old female with DLBCL: whole-body ⁸⁹Zr-Df-crefmirlimab scan 24 hours p.i. (left) at BL and F/U on treatment with paired FDG-PET (right). On BL scans, axial slices of right external iliac mass demonstrate intense uptake of FDG pretreatment, but no BL ⁸⁹Zr-Df-crefmirlimab uptake in tumor sites; however, some marrow uptake plus excretion of catabolized ⁸⁹Zr in bowel is seen. Although the patient had a CMR in RT-treated volume, they had extensive PD out-of-treated volume on treatment. Radiotherapy fields are illustrated on the FDG-PET image. (D) Tumor uptake (SUVmax) of ⁸⁹Zr-Df-crefmirlimab 24 hours p.i. at baseline was significantly higher in patients who achieved a CMR on study (P = .003; adjusted P values ∗P = .01, ∗∗P = .002). D51, 51 days after treatment commencement; ns, not significant; PD, progressive disease; PMR, partial metabolic response.