F-18 labelled 3’-deoxy-3’-fluorothymidine (FLT) positron emission tomography (PET) imaging in patients with advanced pancreatic ductal adenocarcinoma: proof-of-concept reproducibility sub-analysis.
Year: 2016
Session type: Oral
Theme: Diagnosis and therapy
Abstract
Background
The thymidine analogue FLT is transported and phosphorylated in proliferating cells. FLT tumour uptake correlates with proliferation.
Method
Advanced pancreatic ductal adenocarcinoma (PDAC) patients with target lesion >2cm due to start chemotherapy were eligible. Dynamic FLT PET/CT scanning was performed over 60min, before starting chemotherapy (baseline scan, BS). Intra-patient reproducibility was explored by a second FLT scan within 7 days of BS and before chemotherapy (reproducibility scan, RPS). Lesions were manually delineated by two independent radiologists for determination of inter-radiologist concordance. FLT uptake in the primary tumour and metastases was quantified as standardised uptake value (SUV, mean and max) over 45-60min.
Results
Of the 21 patients consented 18 were scanned, all with primary tumour in situ and 83% with distant metastases (60% in liver). Thirty-five FLT scans were acquired for the whole study, 21 scans were analysed for this reproducibility sub-analysis (17 BS, 4 RPS) and 27 lesions delineated. At baseline, median SUVmean and SUVmax were 1.9 (95%CI 1.8-2.1) and 5.9 (95%CI 4.6-7.8), respectively, for the primary (n=17) and 4.6 (95%CI 3.7-5.2) and 8.9 (95%CI 8.2-10.5), respectively, for metastatic lesions (n=10; 9 liver, 1 lymph node). Intra-patient reproducibility between BS and RPS was good (all lesions; n=8): mean change and standard deviation (SD) of test-retest differences and Lin’s concordance coefficient (LCC) for SUVmean (mean change -5.4%; SD 9.8%; LCC 0.947, p<0.001) were superior to SUVmax (mean change 7.9%; SD 19.2%; LCC 0.642, p<0.001). The reproducibility achieved by the second radiologist was similar (6 lesions): SUVmean (mean change -10.3%, SD 12.8%; LCC 0.534, p=0.005) and SUVmax (mean change 4.7%, SD 14.5%; LCC 0.826, p<0.001). Inter-radiologist concordance was assessed by comparing 12 lesions (8 scans; 4 BS, 4 RPS): LCC for SUVmean and SUVmax were 0.635 (p<0.001) and 0.489 (p=0.019), respectively.
Conclusion
FLT-PET is feasible and reproducible (intra-patient and inter-radiologist) in patients with advanced PDAC.