Interim Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography to Predict Pathologic Response to Preoperative Chemoradiotherapy and Prognosis in Patients With Locally Advanced Rectal Cancer.

Abstract Introduction The goal of the present study was to investigate the predictive and prognostic values of interim fluorine-18 (18F) fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) parameters for the prediction of a complete pathologic response (pCR) in patients with locally advanced rectal cancer (LARC) who had received preoperative chemoradiotherapy (PCRT). Patients and Methods A total 103 patients with LARC were included in the present study. All the patients were evaluated by 18F FDG PET/CT before and after 45 Gy of radiotherapy with concurrent oral capecitabine chemotherapy. The quantitative, volumetric parameters and their percentage of change (Δ%) were used to predict the pCR and calculate the overall survival (OS). The predictive value for a pCR of 18F FDG PET/CT cutoff values were determined by receiver operating characteristic analysis. The prognostic significance was assessed using Kaplan-Meier analysis. Results A pCR occurred in 22 patients (21.4%). Univariate and multivariate analyses demonstrated that the post-PCRT maximum standardized uptake value (SUV max2 ) and change in the SUV max (ΔSUV max ) as significant factors for the prediction of pCR, with a sensitivity of 68.2% and specificity of 87.7% and sensitivity of 90.9% and specificity of 80.3%, respectively. Kaplan-Meier analysis showed that a low SUV max2 ( max (≥ 62.2%) were potent predictors for OS. Conclusion The present study has shown the capability of interim 18F FDG PET/CT parameters to predict the achievement of pCR after PCRT in patients with LARC. Of the parameters, SUV max2 and ΔSUV max were potent predictors for pCR and well associated with OS.