Reduction of interobserver variability (IOV) by FDG-PET–based tumor volume delineation (TVD) in radiotherapy planning for pancreatic cancer.

Branagan, Jennifer Mary Rose, Halle, Charlotte and Falk, Stephen , et al. (2013) Reduction of interobserver variability (IOV) by FDG-PET–based tumor volume delineation (TVD) in radiotherapy planning for pancreatic cancer. Journal of Clinical Oncology, 31 (4_suppl). (doi:10.1200/jco.2013.31.4_suppl.229).

Abstract

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 below (Table).

Conclusions: the incorporation of PET scan resulted in a prominent reduction in standard deviation around tumor volumes, smaller largest:smallest GTV ratios and a larger percentage of overlap between investigator volumes, suggesting a reduction in Inter-Observer Variability. PET based RT planning should be considered in multicenter radiotherapy trials in pancreatic cancer to reduce IOV.

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Contributors

Author: Chris Hurt

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