title: International consensus guidelines on Clinical Target Volume delineation in rectal cancer.
abstract: The delineation of Clinical Target Volume (CTV) is a critical step in radiotherapy. Several guidelines suggest different subvolumes and anatomical boundaries in rectal cancer (RC), potentially leading to a misunderstanding in the CTV definition. International consensus guidelines (CG) are needed to improve uniformity in RC CTV delineation.
  
  
  
  The 7 radiation oncologist experts defined a roadmap to produce RC CG. Step 1: revision of the published guidelines. Step 2: selection of RC cases with different clinical stages. Step 3: delineation of cases using Falcon following previously published guidelines. Step 4: meeting in person to discuss the initial delineation outcome, followed by a CTV proposal based on revised and if needed, adapted anatomical boundaries. Step 5: peer review of the agreed consensus. Step 6: peer review meeting to validate the final outcome. Step 7: completion of RC delineation atlases.
  
  
  
  A new ontology of structure sets was defined and the related table of anatomical boundaries was generated. The major modifications were about the lateral lymph nodes and the ischio-rectal fossa delineation. Seven RC cases were made available online as consultation atlases.
  
  
  
  The definition of international CG for RC delineation endorsed by international experts might support a future homogeneous comparison between clinical trial outcomes.
authors.affiliation: Università Cattolica del Sacro Cuore, Radiation Oncology Department, Rome, Italy. Electronic address: vincenzo.valentini@unicatt.it.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Valentini
authors.affiliation: Università Cattolica del Sacro Cuore, Radiation Oncology Department, Rome, Italy. Electronic address: magambacorta@rm.unicatt.it.
authors.forename: Maria Antonietta
authors.initials: MA
authors.lastname: Gambacorta
authors.affiliation: Università Cattolica del Sacro Cuore, Department of Radiological Sciences, Rome, Italy. Electronic address: bbarbaro@rm.unicatt.it.
authors.forename: Brunella
authors.initials: B
authors.lastname: Barbaro
authors.affiliation: Università Cattolica del Sacro Cuore, Radiation Oncology Department, Rome, Italy. Electronic address: vchiloiro@gmail.com.
authors.forename: Giuditta
authors.initials: G
authors.lastname: Chiloiro
authors.affiliation: Università Cattolica del Sacro Cuore, Department of Surgical Science, Rome, Italy. Electronic address: coco_claudio@rm.unicatt.it.
authors.forename: Claudio
authors.initials: C
authors.lastname: Coco
authors.affiliation: University of Texas MD Anderson Cancer Center, Department of Radiation Oncology, Houston, USA. Electronic address: PrajDas@mdanderson.org.
authors.forename: Prajnan
authors.initials: P
authors.lastname: Das
authors.affiliation: University G. D'Annunzio, Gynecologic Oncology Department of Medicine and Aging Sciences, Chieti, Italy. Electronic address: francesco.fanfani@unich.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Fanfani
authors.affiliation: KU Leuven - University of Leuven, Department of Oncology and University Hospitals Leuven, Radiation Oncology, Belgium. Electronic address: ines.joye@uzleuven.be.
authors.forename: Ines
authors.initials: I
authors.lastname: Joye
authors.affiliation: Boston Medical Center, Department of Radiation Oncology, USA. Electronic address: lisa.kachnic@bmc.org.
authors.forename: Lisa
authors.initials: L
authors.lastname: Kachnic
authors.affiliation: Centre Georges-François Leclerc, Department of Radiation Oncology, Dijon, France. Electronic address: PMaingon@cgfl.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Maingon
authors.affiliation: Leiden University Medical Center, Department of Radiation Oncology, The Netherlands. Electronic address: c.a.m.marijnen@lumc.nl.
authors.forename: Corrie
authors.initials: C
authors.lastname: Marijnen
authors.affiliation: Peter MacCallum Cancer Centre, Division of Radiation Oncology and Cancer Imaging, Melbourne, Australia. Electronic address: Sam.Ngan@petermac.org.
authors.forename: Samuel
authors.initials: S
authors.lastname: Ngan
authors.affiliation: KU Leuven - University of Leuven, Department of Oncology and University Hospitals Leuven, Radiation Oncology, Belgium. Electronic address: karin.haustermans@uz.kuleuven.ac.be.
authors.forename: Karin
authors.initials: K
authors.lastname: Haustermans
mesh_terms: D032921:Consensus; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology; D058958:Organs at Risk; D017410:Practice Guidelines as Topic; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology* / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed
keywords: Clinical Target Volume delineation; Consensus guidelines; Rectal cancer