FAPI-PET/CT in Patients with Urothelial Carcinoma: Enfortumab Vedotin and Pembrolizumab vs. Standard Platinum-based Chemotherapy

Ziel/Aim: FAPI-PET may offer improved sensitivity in detecting metastatic urothelial carcinoma (UC). Emerging therapeutic strategies, such as the novel agent enfortumab vedotin in combination with pembrolizumab (EV/P), exhibit enhanced anti-tumor activity in the first-line setting of advanced UC. This study aimed to compare treatment responses using FAPI-PET/CT imaging in UC patients under the EV/P therapy vs. traditional platinum-based chemotherapy (CTx).

Methodik/Methods: Patients with UC and at least two FAPI-PET/CT scans (prior and after initiating systemic therapy, EV/P or CTx) were retrospectively included. Uptake characteristics on FAPI-PET/CT including the uptake intensity (SUVmax) were determined. Additionally, metastatic sites (lymph nodes, bones, visceral organs) were analyzed regarding changes of SUVmax and size (short axis diameter (SAD)) under treatment. Standardized PET (mPERCIST 1.0 based on the SUVmax) as well as CT (RECIST 1.1) response criteria were compared.

Ergebnisse/Results: In total, 17 patients were included (n=8 EV/P, n=9 CTx). SUVmax as well as SAD of ymph node metastases in the CTx group significantly decreased (ΔSUVmax=-3.0; p=0.003; ΔSAD=-0.6 cm; p<0.001). In the EV/P group, however, there was no notable reduction of SAD (ΔSAD=-0.1 cm; p=0.800) while SUVmax decreased (ΔSUVmax=-2.7; p=0.060). A significant decrease of SUVmax was observed in visceral metastases in EV/P patients (ΔSUVmax=-3.9; p=0.001), which was not evident in CTx patients (ΔSUVmax=-0.5; p=0.600). Response assessment by FAPI-PET/CT revealed discordant results compared to CT alone in 9 patients across groups. In the EV/P group, two additional patients were classified progressive by PET, and in the control group one additional patient was classified progressive by PET.

Schlussfolgerungen/Conclusions: FAPI-PET/CT highlights unique treatment responses in advanced UC patients, revealing a significant reduction in FAP expression of visceral metastases with EV/P, while platinum-based chemotherapy shows greater reduction in lymph node size. The discordance between FAPI-PET/CT and conventional imaging results warrants to investigate further the accuracy of FAPI-PET/CT for the detection of disease progression, potentially offering a promising tool for refining response assessment and guiding therapy decisions in advanced UC.

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Artikel online veröffentlicht:
12. März 2025