Same-Day Positron Emission Tomography/Computed Tomography with Ga-Radiolabeled Fibroblast Activation Protein Inhibitors and F-Fluorodeoxyglucose Imaging for Gastrointestinal Cancers.

We investigated the clinical practicability of same-day Ga-radiolabeled fibroblast activation protein inhibitors (Ga-FAPI)-first and F-fluorodeoxyglucose (F-FDG) imaging and compared it with same-day F-FDG-first or 2-day procedures in diagnosing gastrointestinal cancers. Sixty-five patients with confirmed gastrointestinal cancers were divided into same-day Ga-FAPI-first group (Group A), same-day F-FDG-first group (Group B), and 2-day group (Group C). Low-dose CT and low injection activity were performed on Ga-FAPI positron emission tomography/computed tomography (PET/CT). Interval times, radiation dose, diagnostic performance, and detectability were assessed among groups. Additionally, the uptake, tumor-to-liver ratio (TLR), diagnostic efficacy, and TNM stage were compared between the two modalities. The total waiting time for Group C was significantly longer than that for Group A or B (both < 0.001). The total dose-length product and effective dose decreased in all groups. There were comparable detectability and diagnostic performance among groups (all > 0.05). The within-group analysis in Group B indicated that Ga-FAPI PET/CT had higher uptake in the primary and recurrent lesions than F-FDG without differences in TLR, due to higher liver background on Ga-FAPI PET than Group A or C (both < 0.001).Ga-FAPI PET/CT possessed higher accuracy than F-FDG and changed staging in 14 patients (14/65, 21.54%). The same-day Ga-FAPI-first and F-FDG imaging reduced examination waiting time without increased radiation dose, simultaneously achieving excellent diagnostic performance and improving clinical staging in diagnosing gastrointestinal cancers.