title: Definition and delineation of the clinical target volume for rectal cancer.
abstract: OBJECTIVE
  Optimization of radiation techniques to maximize local tumor control and to minimize small bowel toxicity in locally advanced rectal cancer requires proper definition and delineation guidelines for the clinical target volume (CTV). The purpose of this investigation was to analyze reported data on the predominant locations and frequency of local recurrences and lymph node involvement in rectal cancer, to propose a definition of the CTV for rectal cancer and guidelines for its delineation.
  
  
  METHODS
  Seven reports were analyzed to assess the incidence and predominant location of local recurrences in rectal cancer. The distribution of lymphatic spread was analyzed in another 10 reports to record the relative frequency and location of metastatic lymph nodes in rectal cancer, according to the stage and level of the primary tumor.
  
  
  RESULTS
  The mesorectal, posterior, and inferior pelvic subsites are most at risk for local recurrences, whereas lymphatic tumor spread occurs mainly in three directions: upward into the inferior mesenteric nodes; lateral into the internal iliac lymph nodes; and, in a few cases, downward into the external iliac and inguinal lymph nodes. The risk for recurrence or lymph node involvement is related to the stage and the level of the primary lesion.
  
  
  CONCLUSIONS
  Based on a review of articles reporting on the incidence and predominant location of local recurrences and the distribution of lymphatic spread in rectal cancer, we defined guidelines for CTV delineation including the pelvic subsites and lymph node groups at risk for microscopic involvement. We propose to include the primary tumor, the mesorectal subsite, and the posterior pelvic subsite in the CTV in all patients. Moreover, the lateral lymph nodes are at high risk for microscopic involvement and should also be added in the CTV.
authors.affiliation: Department of Radiotherapy, University Hospital Gasthuisberg, Leuven, Belgium.
authors.forename: Sarah
authors.initials: S
authors.lastname: Roels
authors.forename: Wim
authors.initials: W
authors.lastname: Duthoy
authors.forename: Karin
authors.initials: K
authors.lastname: Haustermans
authors.forename: Freddy
authors.initials: F
authors.lastname: Penninckx
authors.forename: Vincent
authors.initials: V
authors.lastname: Vandecaveye
authors.forename: Tom
authors.initials: T
authors.lastname: Boterberg
authors.forename: Wilfried
authors.initials: W
authors.lastname: De Neve
mesh_terms: D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D009364:Neoplasm Recurrence, Local / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy; D010388:Pelvis / Q000000981:diagnostic imaging / Q000473:pathology; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000532:radiotherapy; D012737:Sex Factors; D014057:Tomography, X-Ray Computed