229 Background: Wide IOV has been reported for CT-based TVD during radiotherapy planning for pancreatic cancer (Yamazaki, Anticancer Research 27: 2965-2972, 2007). PET-CT has been successfully incorporated into treatment planning in other tumour sites and has been shown to reduce IOV, but no study has looked at its role in pancreatic radiotherapy. Methods: Six radiation oncologists from 6 oncology centers in the UK were asked to outline GTVs in two cases with pancreatic head tumors. DICOM data set of planning CT, diagnostic CT and FDG-PET-CT scans were made available. GTV was first outlined using the information on the diagnostic CT scan alone, without access to PET scans (GTV_CT). The GTVs were then re-outlined using additional information from the PET scan (GTV_PET). A PTV was grown from the GTV, using a margin of 2cm sup-inf and 1.5cm radially from the GTV, as per standard UK practice. Results: A total of 48 countours (24 GTV contours and 24 PTV contours) were analysed, and the results are presented be...