Assessment of viable tumours by [68Ga]Ga-FAPI-04 PET/CT after local regional treatment in patients with hepatocellular carcinoma

Abstract

Purpose

To investigate the efficacy of [⁶⁸Ga]Ga-FAPI-04 PET/CT for assessing viable tumours (VTs) after local regional treatment (LRT) in hepatocellular carcinoma (HCC) patients. The related imaging features of HCC after LRT are preliminarily discussed.

Methods

A cohort of 37 LRT patients with HCC (encompassing 51 lesions) was retrospectively included from a prospective parent study (ChiCTR2000039099), and sequential PET/CT using [¹⁸F]FDG and [⁶⁸Ga]Ga-FAPI-04 was performed. The diagnostic accuracies of [⁶⁸Ga]Ga-FAPI-04 and [¹⁸F]FDG PET/CT and multiphasic CT/MRI for detecting VTs after LRT were calculated and analysed. Pathological examination was considered the gold standard for VT diagnosis, and clinical follow-up was used as the reference standard. The SUVmax and tumour-to-background ratio (TBR) derived from [¹⁸F]FDG and [⁶⁸Ga]Ga-FAPI-04 PET/CT were calculated and compared. Moreover, the SUVmax, target-to-normal liver ratio (TNR) of VT, tumour necrosis (TN), benign rim (BR), and normal liver (NL) from different imaging modalities after LRT for HCC were compared.

Results

Both the sensitivity (96.0% [24/25] vs. 36.0% [9/25], p < 0.001) and accuracy (94.1%, [48/51] vs. 68.6% [35/51], p = 0.004) of [⁶⁸Ga]Ga-FAPI-04 PET/CT for detecting VTs after LRT were greater than those of [¹⁸F]FDG PET/CT, whereas their specificities were comparable (92.3% [24/26] vs. 100% [26/26]). Notably, [⁶⁸Ga]Ga-FAPI-04 PET/CT had a greater SUVmax (9.80 vs. 3.60) and TBR (9.93 vs. 1.57) than [¹⁸F]FDG PET/CT in VT patients (all p < 0.001). Furthermore, VT had a greater SUVmax and TNR than did TN, BR, and NL on [⁶⁸Ga]Ga-FAPI-04 PET/CT (all p < 0.001) and exhibited morphologic nodular, mass-like, or irregular tracer uptake. Although no significant differences were observed for VT detection (all p > 0.05), [⁶⁸Ga]Ga-FAPI-04 PET/CT and multiphasic CT/MRI complemented each other in some cases.

Conclusion

[⁶⁸Ga]Ga-FAPI-04 PET/CT not only presented higher sensitivity and accuracy than [¹⁸F]FDG PET/CT for diagnosing VTs after LRT for HCC but also showed comparable diagnostic accuracy and complementary roles with multiphasic CT/MRI. Overall, [⁶⁸Ga]Ga-FAPI-04 PET/CT may play an essential role in surveillance after LRT for HCC.

Trial registration

Chinese Clinical Trial Registry ChiCTR2000039099. Registered 17 October 2020.