title: Comparison of four target volume definitions for pancreatic cancer. Guidelines for treatment of the lymphatics and the primary tumor.
abstract: OBJECTIVE
  Target volume definitions for radiotherapy in pancreatic ductal adenocarcinoma (PDAC) vary substantially. Some groups aim to treat the primary tumor only, whereas others include elective lymph nodes (eLNs). eLNs close to the primary tumor are often included unintentionally within the treatment volume, depending on the respective treatment philosophies. We aimed to measure the percentages of anatomical coverage of eLNs by comparing four different contouring guidelines.
  
  
  METHODS
  Planning target volumes (PTVs) were contoured using planning computed tomography (CT) scans of 11 patients with PDAC based on the Oxford, RTOG (Radiation Therapy Oncology Group), Michigan, and SCALOP (Selective Chemoradiation in Advanced Localised Pancreatic Cancer trial) guidelines. Clinical target volumes (CTVs) included the peripancreatic, para-aortic, paracaval, celiac trunk, superior mesenteric, and portal vein lymph node areas. Volumetric comparisons of the coverage of all eLN regions were conducted to illustrate the differences between the four contouring strategies.
  
  
  RESULTS
  The PTV sizes of the RTOG and Oxford guidelines were comparable. The SCALOP and Michigan PTV sizes were similar to each other and significantly smaller than the RTOG and Oxford PTVs. A large variability of eLN coverage was found for the various subregions according to the respective contouring strategies.
  
  
  CONCLUSIONS
  This is the first study to directly compare the percentage of anatomical coverage of eLNs according to four PTVs in the same patient cohort. Potential practical consequences are discussed in detail.
authors.affiliation: Gray Institute for Radiation Oncology and Biology, Department of Oncology, Oxford Cancer Centre, University of Oxford.
authors.forename: E
authors.initials: E
authors.lastname: Fokas
authors.forename: C
authors.initials: C
authors.lastname: Eccles
authors.forename: N
authors.initials: N
authors.lastname: Patel
authors.forename: K-Y
authors.initials: KY
authors.lastname: Chu
authors.forename: S
authors.initials: S
authors.lastname: Warren
authors.forename: W
authors.initials: W
authors.lastname: Gillies McKenna
authors.forename: T B
authors.initials: TB
authors.lastname: Brunner
mesh_terms: D021441:Carcinoma, Pancreatic Ductal / Q000175:diagnosis* / Q000532:radiotherapy* / Q000556:secondary; D005858:Germany; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000592:standards*; D008207:Lymphatic Metastasis; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D017410:Practice Guidelines as Topic; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000592:standards*; D047368:Tumor Burden
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