卵巣癌の診断精度と切除能予測におけるGaGa-FAPI-04 PET/MRとFFDG PET/CTの比較検討

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.

抄録

目的:

卵巣癌の診断および切除可能性評価における[F]fluorodeoxyglucose（[F]FDG）PET/CTと[Ga]Ga-FAPI（fibroblast activating protein inhibitor）PET/MRの臨床応用価値を比較することにより、臨床治療の指針となる理論を提供すること。

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.

方法:

2021年7月から2022年10月までに卵巣悪性腫瘍が臨床的に強く疑われた患者30名を登録し、5日以内に[F]FDG PET/CTと[Ga]Ga-FAPI-04 PET/MRを施行した。20名の患者は、[F]FDG PET/CTと[Ga]Ga-FAPI-04 PET/MRの一貫性を確認するために、[F]FDG PET/CTを一旦終了して[F]FDG PET/MRを受けた。画像はSUVの比較と腹膜癌指標（PCI）およびSUIDANスコアリングシステムによる不完全切除可能性の判断のために分析された。FAP、HK2、Ki67の発現は免疫組織化学染色により解析した。

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.

結果:

PET/MRとPET/CTでは、異なる部位でのSUVに有意差はなく（p>0.05）、診断精度は同等であった。腹膜転移では[Ga]Ga-FAPI-04 PET/MRの方がSUVが高く、診断精度に優位性があった（p<0.01）。また、[Ga]Ga-FAPI-04 PET/MRの感度は、肝臓のSUVが低下したため、腹膜周囲転移の診断に有利であった（p<0.001）。[Ga]Ga-FAPI-04PET/MRは消化管浸潤の診断に有利かもしれない。PCIスコア解析では、[Ga]Ga-FAPI-04 PET/MRは、[F]FDG PET/CTによるスコアの欠落や過小評価を部分的に修正することができたが、左腸周囲転移スコア間のマッチング確率は低く、過大評価しやすかった。興味深いことに、[Ga]Ga-FAPI-04 PET/MRで検出された横隔膜転移は、不完全切除可能性の予測と最大の相関を示した（ロジスティック回帰p=0.02）。免疫組織化学的には、FAPの発現はSUVと強い相関があり（p<0.001）、HK2の発現はSUVと相関があった（p<0.01）。さらに、Ki67≧20％のSUVはKi67＜20％のSUVより有意に高かった（p＜0.05）。

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).

結論:

[Ga]Ga-FAPI-04PET/MRは転移診断に明らかな利点を有し、腫瘍負荷量をより正確に評価し、不完全切除可能性を予測することができた。SUVは腫瘍の悪性度を評価するのに有用であった。

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.