A comparative study of [Ga]Ga-FAPI-04 PET/MR and [F]FDG PET/CT in the diagnostic accuracy and resectability prediction of ovarian cancer.

PURPOSE

To provide a theory for guiding clinical treatment by comparing the clinical application value of [F]fluorodeoxyglucose ([F]FDG) PET/CT and [Ga]Ga-FAPI (fibroblast activating protein inhibitor) PET/MR in the diagnosis and evaluation of resectability of ovarian cancer.

METHODS

Thirty patients with high clinical suspicion of ovarian malignancies were enrolled from July 2021 to October 2022 and underwent [F]FDG PET/CT and [Ga]Ga-FAPI-04 PET/MR within 5 days. Twenty patients underwent [F]FDG PET/MR at once completing [F]FDG PET/CT for consistency checking. Images were analysed for comparing SUVs and for judging incomplete resectability according to the peritoneal cancer index (PCI) and SUIDAN scoring system. The expression of FAP, HK2 and Ki67 was analysed by immunohistochemistry staining.

RESULTS

There was no significant difference between PET/MR and PET/CT in SUVs at different locations (p > 0.05), and their diagnostic accuracies were similar. The diagnostic accuracy of [Ga]Ga-FAPI-04 PET/MR had advantages for peritoneal metastasis since SUVs were higher (p < 0.01). The sensitivity of [Ga]Ga-FAPI-04 PET/MR in the diagnosis of peridiaghragmatic metastases was higher because SUV in the liver was decreased (p < 0.001). [Ga]Ga-FAPI-04 PET/MR might have advantages in diagnosing gastrointestinal invasion. In PCI score analysis, [Ga]Ga-FAPI-04 PET/MR could partially correct missing or underestimated scores by [F]FDG PET/CT, but the matching probability between left peri-intestinal metastasis scores was low and easy to overestimate. Interestingly, diaphragmatic metastasis detected by [Ga]Ga-FAPI-04 PET/MR had the greatest correlation with the prediction of incomplete resectability (logistic regression p = 0.02). Through immunohistochemistry, the expression of FAP had a strong correlation with SUV (p < 0.001), while the expression of HK2 was correlated with SUV (p < 0.01). In addition, SUV with Ki67 ≥ 20% was significantly higher than that with Ki67 < 20% (p < 0.05).

CONCLUSIONS

[Ga]Ga-FAPI-04 PET/MR had obvious advantages for metastases diagnosis and could more accurately assess tumour load and predict incomplete resectability. SUV was conducive to evaluating the degree of tumour malignancy.