SUV^sub max^-based Parameters of FDG-PET/CT Reliably Predict Pathologic Complete Response After Preoperative Hyperthermo-chemoradiotherapy in Rectal Cancer

Background/Aim: To determine the most reliable predictor for pathologic complete response (pCR) in patients who underwent preoperative chemoradiotherapy and regional hyperthermia (HCRT) for rectal cancer. Patients and Methods: Thirty-six patients were enrolled. The local control status of the patients was assessed using 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), magnetic resonance imaging (MRI), and colonoscopy before and after HCRT. The relationships between various parameters of these clinical examinations and pCR were analyzed. Results: Ten (28%) patients achieved pCR. The accuracies of predicting pCR using FDG-PET/CT, MRI, and colonoscopy were 78%, 61%, and 75%, respectively. FDG-PET/CT was the only independent predictive modality for pCR (p=0.021). The maximum standardized uptake value (SUVmax) and SUVmax normalized to liver uptake (SLR) after HCRT showed the highest sensitivity (90%) and the decreasing rate of SUVmax and SLR demonstrated the highest specificity (89%) for pCR. Conclusion: SUVmax-based parameters of FDG-PET/CT after HCRT were the most reliable predictors for pCR.