Longitudinal PET imaging demonstrates biphasic CAR T cell responses in survivors

TLDR

Let's aggregate content. Background sentences: two lines: "Clinical monitoring of adoptive T cell transfer (ACT) utilizes serial blood analyses to discern T cell activity." and "While useful, these data are 1-dimensional and lack spatiotemporal information related to treatment efficacy or toxicity." Combine into one sentence: "Clinical monitoring of adoptive T cell transfer relies on serial blood analyses to detect T cell activity, but these 1‑dimensional data lack spatiotemporal information on treatment efficacy or toxicity." Purpose: from [Purpose, Mechanism] line: "We utilized a human genetic reporter, somatostatin receptor 2 (SSTR2), and PET, to quantitatively and longitudinally visualize whole-body T cell distribution and antitumor dynamics using a clinically approved radiotracer." So purpose: "The study aimed to use SSTR2 and PET to quantitatively and longitudinally visualize whole-body T cell distribution and antitumor dynamics with a clinically approved radiotracer." Mechanism: combine [Mechanism] lines: first line: "SSTR2-based PET was applied to ACT of chimeric antigen receptor (CAR) T cells targeting intercellular adhesion molecule-1, which is overexpressed in anaplastic thyroid tumors." Also the earlier Purpose line includes mechanism but we can incorporate. Mechanism sentence: "SSTR2-based PET was employed to track CAR T cells targeting ICAM‑1 in anaplastic thyroid tumors, enabling whole‑body imaging of T cell distribution and tumor response." Findings: combine all Findings lines: multiple. Summarize: "Initial studies showed SSTR2‑expressing T cells were detectable at low densities with high sensitivity and specificity.

Abstract

Clinical monitoring of adoptive T cell transfer (ACT) utilizes serial blood analyses to discern T cell activity. While useful, these data are 1-dimensional and lack spatiotemporal information related to treatment efficacy or toxicity. We utilized a human genetic reporter, somatostatin receptor 2 (SSTR2), and PET, to quantitatively and longitudinally visualize whole-body T cell distribution and antitumor dynamics using a clinically approved radiotracer. Initial evaluations determined that SSTR2-expressing T cells were detectable at low densities with high sensitivity and specificity. SSTR2-based PET was applied to ACT of chimeric antigen receptor (CAR) T cells targeting intercellular adhesion molecule-1, which is overexpressed in anaplastic thyroid tumors. Timely CAR T cell infusions resulted in survival of tumor-bearing mice, while later infusions led to uniform death. Real-time PET imaging revealed biphasic T cell expansion and contraction at tumor sites among survivors, with peak tumor burden preceding peak T cell burden by several days. In contrast, nonsurvivors displayed unrelenting increases in tumor and T cell burden, indicating that tumor growth was outpacing T cell killing. Thus, longitudinal PET imaging of SSTR2-positive ACT dynamics enables prognostic, spatiotemporal monitoring with unprecedented clarity and detail to facilitate comprehensive therapy evaluation with potential for clinical translation.