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BACKGROUND: The best method of identifying regions within pancreatic tumours that might benefit from an increased radiotherapy dose is not known. We investigated the utility of pre-treatment FDG-PET in predicting the spatial distribution of residual metabolic activity following chemoradiotherapy (CRT) in locally advanced pancreatic cancer (LAPC). METHODS: 17 patients had FDG-PET/CT scans at baseline and six weeks post-CRT. Tumour segmentation was performed at 40% and 50% of SUVmax at baseline and 60%, 70%, 80% and 90% post-CRT. FDG-PET scans were non-rigidly registered to the radiotherapy planning CT using the CT component of the FDG-PET/CT. Percentage overlap of the post-CRT volumes with the pre-CRT volumes with one another and the gross tumour volume (GTV) was calculated. RESULTS: SUVmax decreased during CRT (median pre- 8.0 and post- 3.6, p < 0.0001). For spatial correlation analysis, 9 pairs of scans were included (Four were excluded following complete metabolic response, one patient had a non-FDG avid tumour, one had no post-CRT imaging, one had diffuse FDG uptake that could not be separated from normal tissues and one had an elevated blood glucose). The Pre40% and 50% of SUVmax volumes covered a mean of 50.8% and 30.3% of the GTV respectively. The mean% overlap of the 90%, 80%, 70%, 60% of SUVmax post-CRT with the Pre40% and Pre50% volumes were 83.3%, 84.0%, 83.7%, 77.9% and 77.8%, 69.9%, 74.5%, 64.8% respectively. CONCLUSIONS: Regions of residual metabolic activity following CRT can be predicted from the baseline FDG-PET and could aid definition of a biological target volume for non-uniform dose prescriptions.

Original publication

DOI

10.1186/1748-717X-9-146

Type

Journal article

Journal

Radiat Oncol

Publication Date

24/06/2014

Volume

9

Keywords

Adenocarcinoma, Antineoplastic Combined Chemotherapy Protocols, Chemoradiotherapy, Cisplatin, Clinical Trials, Phase II as Topic, Deoxycytidine, Fluorodeoxyglucose F18, Follow-Up Studies, Humans, Multimodal Imaging, Neoplasm Staging, Pancreatic Neoplasms, Positron-Emission Tomography, Prognosis, Radiopharmaceuticals, Radiotherapy Dosage, Radiotherapy Planning, Computer-Assisted, Tomography, X-Ray Computed