Comparison of 11C-Acetate and 18F-FDG PET/CT for Immune Infiltration and Prognosis in Hepatocellular Carcinoma.

Immunotherapy has revolutionized cancer treatment, making it a challenge to noninvasively monitor immune infiltration. Metabolic reprogramming in cancers, including hepatocellular carcinoma (HCC), is closely linked to immune status. In this study, we aimed to evaluate the ability of carbon-11 acetate (¹¹C-acetate) and fluorine-18 fluorodeoxyglucose (¹⁸F-FDG) PET/CT findings in predicting overall survival (OS) and immune infiltration in HCC patients. Totally 32 patients who underwent preoperative ¹⁸F-FDG and ¹¹C-acetate PET/CT, followed by liver resection for HCC, were prospectively enrolled at authors' institute between January 2019 and October 2021. Tracer uptake was qualified. Densities of CD3⁺, CD8⁺, and granzyme B⁺ CD8⁺ immune cells were assessed and the Immunoscore was defined by combining the densities of CD3⁺ and CD8⁺ in tumor interior (TI) and invasion margin (IM). Patients with avid HCCs in ¹¹C-acetate PET/CT demonstrated a longer OS. Those with only ¹¹C-acetate-avid HCCs exhibited a longer OS compared to those with only ¹⁸F-FDG uptake. In contrast to ¹⁸F-FDG uptake, ¹¹C-acetate uptake was positively associated with CD3⁺, CD8⁺, and granzyme B⁺ CD8⁺ cell infiltration. Patients with a higher Immunoscore exhibited a longer OS and an increased uptake of ¹¹C-acetate rather than ¹⁸F-FDG. The sensitivity of ¹¹C-acetate PET/CT in the detection of patients with immune infiltration was superior to that of ¹⁸F-FDG PET/CT (88% [21 of 24] vs. 58% [14 of 24]). These data show that preoperative ¹¹C-acetate PET/CT may be a promising approach for the evaluation of immune status and postoperative outcome of HCCs.