title: Postoperative radiotherapy for prostate cancer: a comparison of four consensus guidelines and dosimetric evaluation of 3D-CRT versus tomotherapy IMRT.
abstract: OBJECTIVE
  Despite the benefits of adjuvant radiotherapy after radical prostatectomy, approximately one-half of patients relapse. Four consensus guidelines have been published (European Organization for Research and Treatment of Cancer, Faculty of Radiation Oncology Genito-Urinary Group, Princess Margaret Hospital, Radiation Therapy Oncology Group) with the aim of standardizing the clinical target volume (CTV) delineation and improve outcomes. To date, no attempt has been made to compare these guidelines in terms of treatment volumes or organ at risk (OAR) irradiation. The extent to which the guideline-derived plans meet the dosimetric constraints of present trials or of the Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) trial is also unknown. Our study also explored the dosimetric benefits of intensity-modulated radiotherapy (IMRT).
  
  
  METHODS
  A total of 20 patients treated with postoperative RT were included. The three-dimensional conformal radiotherapy (3D-CRT) plans were applied to cover the guideline-generated planning target volumes (66 Gy in 33 fractions). Dose-volume histograms (DVHs) were analyzed for CTV/planning target volume coverage and to evaluate OAR irradiation. The OAR DVHs were compared with the constraints proposed in the QUANTEC and Radiotherapy and Androgen Deprivation In Combination After Local Surgery (RADICALS) trials. 3D-CRT plans were compared with the tomotherapy plans for the Radiation Therapy Oncology Group planning target volume to evaluate the advantages of IMRT.
  
  
  RESULTS
  The CTV differed significantly between guidelines (p < 0.001). The European Organization for Research and Treatment of Cancer-CTVs were significantly smaller than the other CTVs (p < 0.001). Differences in prostate bed coverage superiorly accounted for the major volumetric differences between the guidelines. Using 3D-CRT, the DVHs rarely met the QUANTEC or RADICALS rectal constraints, independent of the guideline used. The RADICALS bladder constraints were met most often by the European Organization for Research and Treatment of Cancer consensus guideline (14 of 20). The tomotherapy IMRT plans resulted in significant OAR sparing compared with the 3D-CRT plans; however, the RADICALS and QUANTEC criteria were still missed in a large percentage of cases.
  
  
  CONCLUSIONS
  Treatment volumes using the current consensus guidelines differ significantly. For the four CTV guidelines, the rectal and bladder DVH constraints proposed in the QUANTEC and RADICALS trials are rarely met with 3D-CRT. IMRT results in significant OAR sparing; however, the RADICALS dose constraints are still missed for a large percentage of cases. The rectal and bladder constraints of RADICALS should be modified to avoid a reduction in the CTVs.
authors.affiliation: Division of Radiation Oncology, Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada. smalone@ottawahospital.on.ca
authors.forename: Shawn
authors.initials: S
authors.lastname: Malone
authors.forename: Jennifer
authors.initials: J
authors.lastname: Croke
authors.forename: Nicolas
authors.initials: N
authors.lastname: Roustan-Delatour
authors.forename: Eric
authors.initials: E
authors.lastname: Belanger
authors.forename: Leonard
authors.initials: L
authors.lastname: Avruch
authors.forename: Colin
authors.initials: C
authors.lastname: Malone
authors.forename: Christopher
authors.initials: C
authors.lastname: Morash
authors.forename: Cathleen
authors.initials: C
authors.lastname: Kayser
authors.forename: Kathryn
authors.initials: K
authors.lastname: Underhill
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Kyle
authors.initials: K
authors.lastname: Malone
authors.forename: Balazs
authors.initials: B
authors.lastname: Nyiri
authors.forename: Johanna
authors.initials: J
authors.lastname: Spaans
mesh_terms: D000368:Aged; D002986:Clinical Trials as Topic / Q000592:standards; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D011184:Postoperative Period; D017410:Practice Guidelines as Topic; D011467:Prostate / Q000473:pathology; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D018714:Radiotherapy, Adjuvant; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods; D012007:Rectum / Q000000981:diagnostic imaging / Q000528:radiation effects; D016879:Salvage Therapy / Q000379:methods; D047368:Tumor Burden; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000528:radiation effects