Background: 3'-Deoxy-3'-[18F]fluorothymidine ([18F]FLT) PET has limited utility in abdominal imaging due to high physiological hepatic uptake of a tracer. We evaluated [18F]FLT-PET/CT combined with a temporal-intensity information-based voxel-clustering approach termed kinetic spatial filtering (KSF) to improve tumour visualisation in patients with locally advanced and metastatic gastro-oesophageal cancer and as a marker of early response to chemotherapy. Dynamic [18F]FLT-PET/CT data were collected before and 3 weeks post first cycle of chemotherapy. Changes in tumour [18F]FLT-PET/CT variables were determined. Response was determined on contrast-enhanced CT after three cycles of therapy using RECIST 1.1.
Results: Ten patients were included. Following application of the KSF, visual distinction of all oesophageal and/or gastric tumours was observed in [18F]FLT-PET images. Among the nine patients available for response evaluation (RECIST 1.1), three patients had responded (partial response) and six patients were non-responders (stable disease). There was a significant association between Ki-67 and all baseline [18F]FLT-PET parameters. Area under the curve (AUC) from 0 to 1 min was associated with treatment response.
Conclusions: The results of this study indicate that application of the KSF allowed accurate visualisation of both primary and metastatic lesions following imaging with the proliferation marker, [18F]FLT-PET/CT. However, [18F]FLT-PET uptake parameters did not correlate with response. Instead, we observe significant changes in tracer delivery following chemotherapy suggesting that further [18F]FLT-PET/CT studies in this tumour type should be undertaken with caution.
Keywords: Chemotherapy; Early response; Gastro-oesophageal cancer; RECIST 1.1; [18 F]FLT-PET.