title: Influence of number of CAG repeats on local control in the RTOG 86-10 protocol.
abstract: OBJECTIVE
  The number of CAG repeats on the androgen receptor (AR) gene is inversely proportional to transcriptional activity. The purpose of this study was to determine if short-term androgen deprivation therapy (RT + HT) can improve outcome in patients with tumors with short CAG repeats (<19).
  
  
  METHODS
  Prostate cancer patients were randomized to receive either radiotherapy (RT) alone or (RT + HT) in the RTOG 86-10 study. CAG repeats were measured in 94 tumor specimens (21%; test cohort) of the 456 (parent cohort) analyzable cases. AR flow cytometry measurements were done on 13 patients. The effect on local failure (LF), distant metastases (DM), prostate cancer survival (PSS), and overall survival (OS) was studied.
  
  
  RESULTS
  Pretreatment characteristics and assigned treatment arm were not significantly different between the parent and test groups except for a significantly higher risk of death (P = 0.049) in the test group. The median CAG repeat was 19. There were no significant differences in stage, or Gleason score between high (19 or greater) and low CAG (<19) patients within each treatment group. Number of CAG repeats alone did not significantly influence LF, DM, PSS, and OS. However, when the CAG repeat outcome was studied in conjunction with androgen deprivation therapy, patients with CAG <19 who received H + RT had improved local control as compared with patients who received RT alone (P = 0.026, 5-year rates 4.6% versus 36.4%) and improved local control over patients with CAG > or =19 that received H + RT (P = 0.028).
  
  
  CONCLUSIONS
  Patients with short CAG repeats show a local control benefit with short-term androgen deprivation therapy, but no improvement in survival.
authors.affiliation: Department of Radiation Oncology, University of Miami School of Medicine, Miami, FL 33136, USA. mwahab@med.miami.edu
authors.forename: May
authors.initials: M
authors.lastname: Abdel-Wahab
authors.forename: Brian A
authors.initials: BA
authors.lastname: Berkey
authors.forename: Awtar
authors.initials: A
authors.lastname: Krishan
authors.forename: Tom
authors.initials: T
authors.lastname: O'Brien
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Hammond
authors.forename: Mack
authors.initials: M
authors.lastname: Roach
authors.forename: Colleen
authors.initials: C
authors.lastname: Lawton
authors.forename: Milijenko
authors.initials: M
authors.lastname: Pilepich
authors.forename: Arnold
authors.initials: A
authors.lastname: Markoe
authors.forename: Alan
authors.initials: A
authors.lastname: Pollack
mesh_terms: D000726:Androgen Antagonists / Q000627:therapeutic use; D003131:Combined Modality Therapy; D005434:Flow Cytometry; D017273:Goserelin / Q000627:therapeutic use; D006801:Humans; D008297:Male; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000532:radiotherapy*; D011944:Receptors, Androgen / Q000235:genetics*; D016019:Survival Analysis; D016896:Treatment Outcome; D018911:Trinucleotide Repeats
chemical_list: D000726:Androgen Antagonists; D011944:Receptors, Androgen; D017273:Goserelin