title: Conformity analysis to demonstrate reproducibility of target volumes for Margin-Intense Stereotactic Radiotherapy for borderline-resectable pancreatic cancer.
abstract: Margin-directed neoadjuvant radiotherapy for borderline-resectable pancreatic cancer (BRPC) aims to facilitate clear surgical margins. A systematic method was developed for definition of a boost target volume prior to a formal phase-I study.
  
  
  
  Reference structures were defined by two oncologists and one radiologist, target structures were submitted by eight oncologist investigators and compared using conformity indices. Resultant risk of duodenal bleed (NTCP) was modelled.
  
  
  
  For GTV, reference volume was 2.1cm3and investigator mean was 6.03cm3(95% CI 3.92-8.13cm3), for boost volume 1.1cm3and 1.25cm3(1.02-1.48cm3). Mean Dice conformity coefficient for GTV was 0.47 (0.38-0.56), and for boost volume was significantly higher at 0.61 (0.52-0.70, p=0.01). Discordance index (DI) for GTV was 0.65 (0.56-0.75) and for boost volume was significantly lower at 0.39 (0.28-0.49, p=0.001). NTCP using reference contours was 2.95%, with mean for investigator contour plans 3.93% (3.63-4.22%). Correlations were seen between NTCP and GTV volume (p=0.02) and NTCP and DI (correlation coefficient 0.83 (0.29-0.97), p=0.01).
  
  
  
  Better conformity with reference was shown for boost volume compared with GTV. Investigator GTV volumes were larger than reference, had higher DI scores and modelled toxicity risk. A consistent method of target structure definition for margin-directed pancreatic radiotherapy is demonstrated.
authors: CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, UK; The Churchill Hospital, Oxford, UK.
authors: Daniel L P
authors: DL
authors: Holyoake
authors: CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, UK; The Churchill Hospital, Oxford, UK.
authors: Maxwell
authors: M
authors: Robinson
authors: The Beatson West of Scotland Cancer Centre, Glasgow, UK.
authors: Derek
authors: D
authors: Grose
authors: The Beatson West of Scotland Cancer Centre, Glasgow, UK.
authors: David
authors: D
authors: McIntosh
authors: University of Leeds, CRUK Leeds Centre, UK; Leeds Cancer Centre, St James's University Hospital, Leeds, UK.
authors: David
authors: D
authors: Sebag-Montefiore
authors: Leeds Cancer Centre, St James's University Hospital, Leeds, UK.
authors: Ganesh
authors: G
authors: Radhakrishna
authors: The Churchill Hospital, Oxford, UK.
authors: Neel
authors: N
authors: Patel
authors: CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, UK.
authors: Mike
authors: M
authors: Partridge
authors: CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, UK; The Churchill Hospital, Oxford, UK.
authors: Somnath
authors: S
authors: Mukherjee
authors: CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, UK; The Churchill Hospital, Oxford, UK. Electronic address: maria.hawkins@oncology.ox.ac.uk.
authors: Maria A
authors: MA
authors: Hawkins
mesh_terms: D006801:Humans; D020360:Neoadjuvant Therapy / Q000379:methods; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D049268:Positron-Emission Tomography; D016634:Radiosurgery / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
keywords: Borderline-resectable; Pancreatic cancer; Radiation therapy quality assurance; SBRT; Target volume definition