[18F]FAPI PET/CT in the evaluation of focal liver lesions with [18F]FDG non-avidity.

PURPOSE: This prospective study was aimed to investigate the potential utility of [18F]fibroblast activation protein inhibitor (FAPI) PET/CT for evaluating focal liver lesions (FLLs) with [18F]FDG non-avidity. METHODS: From January 2021 to March 2022, this prospective study included 80 FLLs that were not avid on [18F]FDG PET/CT from 37 patients, then underwent [18F]FAPI PET/CT. All patients with FLL(s) with biopsy-proof or follow-up confirmation were categorized into four subgroups (20 hepatocellular carcinomas [HCCs]/5 non-HCC malignancies/4 inflammatory FLLs/8 benign noninflammatory FLLs). The diagnostic value of [18F]FAPI for detecting liver malignancy was determined by visual evaluation. Differences in the maximum standardized uptake value (SUVmax) and lesion-to-background ratio (LBR) obtained from [18F]FAPI PET/CT among the four subgroups were analyzed by semiquantitative analysis. RESULTS: Among the thirty-seven enrolled participants (34 males; median age 57 years, range 48-67 years), on visual evaluation, the sensitivity, specificity, and accuracy of [18F]FAPI PET for detecting liver malignancy in the patient-based analysis were 96.0% (24/25), 58.3% (7/12), and 83.8% (31/37), respectively. On semiquantitative analysis, the SUVmax and LBR of [18F]FAPI PET in liver malignancy (33 HCC lesions; 19 non-HCC malignant lesions) were significantly higher than those in 11 benign noninflammatory FLLs [HCC: SUVmax: 6.4 vs. 4.5, P = 0.017; LBR: 5.1 vs. 1.5, P = 0.003; non-HCC: SUVmax: 5.5 vs. 4.5, P = 0.008; LBR: 4.4 vs. 1.5, P = 0.042]. Notably, there was no significant difference in the SUVmax of [18F]FAPI PET between 33 HCC lesions and 17 inflammatory FLLs (6.4 vs. 8.2, P = 0.37), but the LBR of [18F]FAPI PET in HCC were significantly lower than that in inflammatory FLLs (5.1 vs. 9.1, P = 0.003). CONCLUSIONS: [18F]FAPI PET/CT shows high sensitivity in detecting HCC and non-HCC malignancy with [18F]FDG non-avidity. [18F]FAPI might be a promising radiopharmaceutical for the differential diagnosis of benign noninflammatory FLLs and liver malignancy with [18F]FDG non-avidity.

18 F-FDG PET/CT Versus 18 F-FAPI PET/CT in a Case of Recurrent Malignant Phyllodes Breast Tumor.

ABSTRACT: A 52-year-old woman with medical history of surgery for left malignant phyllodes breast tumor found a mass on the left chest 3 months ago. A suspicion of recurrent malignant phyllodes breast tumor was made. The patient was enrolled in the clinical trial of 18 F-FAPI PET/CT in recurrent sarcoma (no. NCT05485792). 18 F-FAPI PET/CT and 18 F-FDG PET/CT were performed, and the images demonstrated intense uptake in a huge mass in the left anterior chest wall. Then the patient underwent extended resection of left chest wall tumor. The tumor proved to be recurrent malignant phyllodes breast tumor pathologically.

Role of [18F]FAPI-04 in staging and therapeutic management of intrahepatic cholangiocarcinoma: prospective comparison with [18F]FDG PET/CT.

BACKGROUND: Fluorine-18 fluorodeoxyglucose ([18F]FDG) positron emission tomography/computed tomography (PET/CT) has some limitations in diagnosis of Intrahepatic cholangiocarcinoma (ICC). MATERIALS AND METHODS: Patients with histologically confirmed ICC who underwent both [18F]FDG and 18F-labeled fibroblast-activation protein inhibitors ([18F]FAPI)-04 PET/CT were prospectively analyzed. The maximum standard uptake value (SUVmax), tumor-to-background ratio (TBR), metabolic tumor volume (MTV), total lesion glycolysis (TLG), [18F]FAPI-avid tumor volume (FTV), total lesion fibroblast activation protein expression (TLF) were compared between the two modalities by paired Wilcoxon signed-rank test and Mann-Whitney U test, and McNemar's test was used to assess the diagnostic accuracy between the two techniques. RESULTS: In total, 23 patients with 389 lesions were included. Compared to [18F]FDG, [18F]F-FAPI-04 PET/CT demonstrated a higher detection rate for intrahepatic lesions (86.3% vs. 78.2% P = 0.040), lymph node metastases (85.2% vs. 68.2%, P = 0.007), peritoneal metastases (100% vs. 93.8%), and bone metastases (100% vs. 70.5%, P < 0.001). [18F]FAPI-04 PET showed higher SUVmax, TBR and greater tumor burden values than [18F]FDG PET in non-cholangitis intrahepatic lesions (SUVmax: 8.7 vs. 6.4, P < 0.001; TBR: 8.0 vs. 3.5, P < 0.001; FTV vs. MTV: 41.3 vs. 12.4, P < 0.001; TLF vs. TLG: 223.5 vs. 57.0, P < 0.001), lymph node metastases (SUVmax: 6.5 vs. 5.5, P = 0.042; TBR: 5.4 vs. 3.9, P < 0.001; FTV vs. MTV: 2.0 vs. 1.5, P = 0.026; TLF vs. TLG: 9.0 vs. 7.8 P = 0.024), and bone metastases (SUVmax: 9.7 vs. 5.25, P < 0.001; TBR: 10.8 vs. 3.0, P < 0.001; TLF vs. TLG: 9.8 vs. 4.2, P < 0.001). However, [18F]FDG showed higher radiotracer uptake (SUVmax: 14.7 vs. 8.4, P < 0.001; TBR: 7.4 vs. 2.8, P < 0.001) than [18F]FAPI-04 PET/CT for 6 patients with obstructive cholangitis. [18F]FAPI-04 PET/CT yielded a change in planned therapy in 6 of 23 (26.1%) patients compared with [18F]FDG. CONCLUSIONS: [18F]FAPI-04 PET/CT had higher detection rate and radiotracer uptake than [18F]FDG PET/CT in intrahepatic lesions, lymph node metastases, and distant metastases, especially in bone. Therefore, [18F]FAPI-04 PET/CT may be a promising technique for diagnosis and staging of ICC. TRIAL REGISTRATION: Clinical Trials, NCT05485792. Registered 1 August 2022, retrospectively registered, https//clinicaltrials.gov/study/NCT05485792?cond=NCT05485792&rank=1.

Head-to-head comparison of 18F-FAPI and 18F-FDG PET/CT in staging and therapeutic management of hepatocellular carcinoma.

BACKGROUND: Fluorine 18 (18F) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) has limitations in staging hepatocellular carcinoma (HCC). The recently introduced 18F-labeled fibroblast-activation protein inhibitor (FAPI) has shown promising prospects in detection of HCC lesions. This study aimed to investigate the initial staging and restaging performance of 18F-FAPI PET/CT compared to 18F-FDG PET/CT in HCC. METHODS: This prospective study enrolled histologically confirmed HCC patients from March 2021 to September 2022. All patients were examined with 18F-FDG PET/CT and 18F-FAPI PET/CT within 1 week. The maximum standard uptake value (SUVmax), tumor-to-background ratio (TBR), and diagnostic accuracy were compared between the two modalities. RESULTS: A total of 67 patients (57 men; median age, 57 [range, 32-83] years old) were included. 18F-FAPI PET showed higher SUVmax and TBR values than 18F-FDG PET in the intrahepatic lesions (SUVmax: 6.7 vs. 4.3, P < 0.0001; TBR: 3.9 vs. 1.7, P < 0.0001). In diagnostic performance, 18F-FAPI PET/CT had higher detection rate than 18F-FDG PET/CT in intrahepatic lesions [92.2% (238/258) vs 41.1% (106/258), P < 0.0001] and lymph node metastases [97.9% (126/129) vs 89.1% (115/129), P = 0.01], comparable in distant metastases [63.6% (42/66) vs 69.7% (46/66), P > 0.05]. 18F-FAPI PET/CT detected primary tumors in 16 patients with negative 18F-FDG, upgraded T-stages in 12 patients and identified 4 true positive findings for local recurrence than 18F-FDG PET, leading to planning therapy changes in 47.8% (32/67) of patients. CONCLUSIONS: 18F-FAPI PET/CT identified more primary lesions, lymph node metastases than 18F-FDG PET/CT in HCC, which is helpful to improve the clinical management of HCC patients. TRIAL REGISTRATION: Clinical Trials, NCT05485792 . Registered 1 August 2022, Retrospectively registered.