title: Comparing CTVs for permanent prostate brachytherapy.
abstract: OBJECTIVE
  To delineate the clinical target volume (CTV) in low dose rate (LDR) brachytherapy for prostate cancer, American Brachytherapy Society (ABS) recommends a CTV = prostate. ESTRO advocates a CTV = prostate + 3 mm excluding rectum and many authors use and recommend other different CTVs. This study aims to: (1) evaluate the appropriateness of these recommendations and (2) test the applicability of seed distributions on the different CTVs and contrast the dosimetric differences.
  
  
  METHODS
  Ninety-eight patients treated with (125)I seeds (dose 145 Gy; CTV = prostate) were studied. We established for every patient: (1) risk of extraprostatic extension (EPE), (2) adequacy of original plan to an extended CTV with 3 mm-margin (3) a new planning and seed distribution for this CTV and (4) comparison of dosimetry of both plans.
  
  
  RESULTS
  Mean risk of EPE was 28.46 %. Original plan, when applied to the extended CTV, resulted in unsatisfactory dosimetry. A plan was generated for the 98 extended CTVs meeting all dosimetric specifications.
  
  
  CONCLUSIONS
  The risk of EPE is high enough to consider a 3 mm-margin around prostate necessary for all cases. A CTV = prostate + 3 mm except rectum as ESTRO recommends is feasible and would adjust planning to the most probable extension of the tumor.
authors.affiliation: Department of Radiation Oncology, University of La Laguna Tenerife, Santa Cruz de Tenerife, Spain, caoton@gmail.com.
authors.forename: C A
authors.initials: CA
authors.lastname: Oton
authors.forename: L
authors.initials: L
authors.lastname: Blanco
authors.forename: L F
authors.initials: LF
authors.lastname: Oton
authors.forename: S
authors.initials: S
authors.lastname: Moral
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk; D017410:Practice Guidelines as Topic; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012007:Rectum; D014521:Urethra
chemical_list: D007457:Iodine Radioisotopes