The Role of18F-FLT PET/CT in Assessing Early Response to Transarterial Radioembolization and Chemoembolization in Patients with Primary and Metastatic Liver Tumors; [Primer ve Metastatik Karaciğer Tümörlü Hastalarda Transarteriyel Radyoembolizasyon ve Kemoembolizasyona Erken Yanıtı Değerlendirmede18F-FLT PET/BT’nin Rolü]

Objectives: Metastases and primary malignancies are common in the liver. Local ablative applications such as transarterial chemoembolization (TACE), and transarterial radioembolization (TARE) provide minimally invasive and safe treatment in unresectable liver tumors. Early detection of response to treatment prevents unnecessary toxicity and cost in non-responder patients and provides an earlier use of other options that may be effective. This study aimed to identify the role of18F-fluorothymidine (FLT) positron emission tomography/computed tomography (PET/CT) in the assessment of early response to TACE and TARE treatments in patients with unresectable primary and metastatic liver tumors. Methods: This single-center study included 63 patients who underwent18F-FLT PET/CT for response evaluation after TACE and TARE. After excluding 20 patients whose data were missing 43 TARE-receiving patients were analyzed. The compatibility of change in semi-quantitative values obtained from the18F-FLT PET/CT images with the treatment responses detected in18F-fluorodeoxyglucose PET/CT, CT, and MR images and survival was evaluated. Results: There was no correlation between early metabolic, morphological response, and18F-FLT uptake pattern, and change in standardized uptake values (SUV) which were ΔSUVmax, ΔSUVmean, ΔSUVpeak., ΔSUVmean, ΔSUVpeak values. There was no significant correlation between18F-FLT uptake pattern, ΔSUVmax, ΔSUVmean, ΔSUVpeak, and overall survival, progression-free survival (PFS) for the target lobe PFS for the whole-body. The survival distributions for the patients with >30% change in ΔSUVmax and ΔSUVpeak values were statistically significantly longer than the patients with <30% change (p<0.009 and p<0.024, respectively). Conclusion: There was significant longer PFS for target liver lobe in patients with more than 30% decrease in18F-FLT SUVmax and SUVpeak of the liver lesion in primary and metastatic unresectable liver tumors undergoing TARE. © 2022 by Turkish Society of Nuclear Medicine.