227 - Pathologic Response Prediction Value of ¹⁸f-Fapi PET/CT in ESCC Treated with Neoadjuvant Camrelizumab and Chemotherapy: A Phase II Clinical Trial

Y. Wei¹, Y. Dong², and J. Yu³; ¹Department of Radiation Oncology and Shandong Provincial Key Laboratory of Radiation Oncology, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, ²Department of Radiation Oncology and Shandong Provincial Key Laboratory of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and ShandongShandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, ³Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China

Purpose/Objective(s): The neoadjuvant therapy of immunotherapy combined with chemotherapy has brought safer and more effective treatment for locally advanced esophageal squamous cell carcinomas (LA-ESCC) patients, but there are still 55% to 83% of patients with poor curative effect. This study was a single-center, single-arm, phase II trial (ChiCTR2100050057), evaluating the predict value of novel tumor stromal cell imaging agent, ¹⁸F-FAPI PET/CT in camrelizumab plus chemotherapy in the neoadjuvant treatment for LA-ESCC patients. Materials/

Methods: This study included thirty-two patients with newly diagnosed LA-ESCC who underwent ¹⁸F-FAPI PET/CT at baseline and after 2 cycles of neoadjuvant camrelizumab and chemotherapy (nCC). TBRmax, TBRpeak, TBRmean, metabolic tumor volume (MTV) and total lesion FAP expression (TLF) on PET, and PD-L1 expression were recorded. Patients were classified as major or minor pathologic responders (MPR or MiPR) according to postoperative pathology findings. We compared the PET parameters between the 2 pathologic response groups and analyzed their predictive performance for tumor pathologic response.
Results: 59.38% (19/32) achieved an MPR, and 40.62% (13/32) was MiPR. Patients with MPR found higher ¹⁸F-FAPI uptakes (TBRmax, TBRpeak, and TBRmean) than MiPR, all P values <0.05, but TLF and MTV found no difference. For predicting MPR, the optimal cutoff values for TBRmax, TBRpeak, and TBRmean were 12.37 (AUC, 0.77; P=0.009), 9.84 (AUC, 0.73; P=0.027), and 6.30 (AUC, 0.75; P=0.016), respectively. No significant difference was observed in PD-L1 expression between MPR and MiPR, 9.44±17.72 vs 2.33±4.36, P=0.145. No correlation was found between PD-L1 expression and TBRmax, TBRpeak, and TBRmean, MTV or TLF, all P values >0.05.
Conclusion: In this study, TBRmax, TBRpeak, and TBRmean of ¹⁸F-FAPI PET at baseline may be better predictors of nCC for LA-ESCC. These findings may help optimize the Ncc treatment for patients with LA-ESCC.