The role of 18F-FDG PET/CT in predicting the pathological response to neoadjuvant PD-1 blockade in combination with chemotherapy for resectable esophageal squamous cell carcinoma

Abstract

Purpose: Accurate assessment of residual disease of tumor and lymph nodes after neoadjuvant immunochemotherapy is crucial in the active surveillance for patients with pathological complete response (pCR) and the optimal extent of lymphadenectomy for patients with non-pCR. This post hoc analysis aimed to evaluate the performance of ¹⁸F-FDG PET/CT to predict the pathological response to neoadjuvant immunochemotherapy for esophageal squamous cell carcinoma (ESCC).

Methods: Fifty-eight resectable ESCC patients received two cycles of camrelizumab in combination with chemotherapy and were enrolled in the final analysis. The ¹⁸F-FDG PET/CT scans were acquired at baseline (scan-1) and after immunochemotherapy but prior to surgery (scan-2). Maximum standardized uptake value (SUV_max), mean standardized uptake value (SUV_mean), tumor-to-blood pool SUV_max ratio (SUV_TBR), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were evaluated for their association with the pathological response to immunochemotherapy.

Results: Nineteen patients (32.8%, 19/58) had pCR and thirty-nine patients (67.2%, 39/58) had non-pCR after two doses of camrelizumab and chemotherapy. At scan-2, the SUV_max, SUV_mean, SUV_TBR, TLG, and MTV were significantly lower in pCR than in non-pCR patients. Decrease in TLG and MTV between scan-2 and scan-1 of the same patient was significantly higher in the pCR than in the non-pCR group. In the receiver operating characteristic curve analysis, SUV_max, SUV_mean, SUV_TBR, TLG, and MTV in scan-2 showed excellent predictive value for the pCR of primary tumors. Furthermore, SUV_max in scan-2 were higher in positive lymph nodes than in negative ones, suggesting a high negative predictive ability (98.6%) with a cut-off value at 1.4.

Conclusion: The parameters of ¹⁸F-FDG PET/CT have the excellent performance for predicting pCR after the combined neoadjuvant immunochemotherapy in resectable ESCC.

Trial registration: ChiCTR2000028900. Registered on January 6, 2020.

Keywords: 18F-FDG PET/CT; Esophageal squamous cell carcinoma; Neoadjuvant therapy; PD-1 blockade; Pathological response.