title: Predictors of androgen deprivation therapy efficacy combined with prostatic irradiation: the central role of tumor stage and radiation dose.
abstract: OBJECTIVE
  To evaluate the response of clinically localized prostate cancer to various durations of planned androgen deprivation therapy (ADT) and to investigate subgroups predicting response.
  
  
  METHODS
  Data of 3,666 prostate cancer patients treated with either combined ADT and external beam radiotherapy (EBRT) or EBRT alone at four institutions were examined. ADT consisted of neoadjuvant, concurrent, or adjuvant ADT or combinations of these regimens. The primary endpoint was time to biochemical failure (nadir plus 2 ng/ml), assessed from the end of therapy. Factors predictive for the need for ADT were examined with interaction analyses.
  
  
  RESULTS
  The impact of increasing ADT duration was nonlinear with, on average, 6 months of adjuvant ADT resulting in a reduction of the risk of biochemical failure by 38% (95% confidence interval [CI], 29%-46%), while 12, 24, and 36 months of ADT resulted in a 58% (95% CI, 47%-67%), 66% (95% CI, 55%-75%), and 66% (95% CI, 51%-77%) relative failure reduction, respectively. Patients with higher T stage cancers and those treated with lower radiation doses had a significantly greater benefit for increasing ADT duration (interaction, p=0.016 and p=0.007, respectively). Pretreatment prostate-specific antigen values, Gleason score, age, and risk group did not modify the response to ADT.
  
  
  CONCLUSIONS
  The known ADT efficacy derived from randomized studies can be generalized to patients with different features, and individual predictions of potential benefit from ADT use and duration may be calculated to aid patient and physician decision making. Tumor stage and radiation dose variations were related to significantly different ADT duration effects. The validity of these predictive factors requires prospective evaluation.
authors.affiliation: Peter MacCallum Cancer Centre and University of Melbourne, Melbourne, Australia. scott.williams@petermac.org
authors.forename: Scott
authors.initials: S
authors.lastname: Williams
authors.forename: Mark
authors.initials: M
authors.lastname: Buyyounouski
authors.forename: Larry
authors.initials: L
authors.lastname: Kestin
authors.forename: Gillian
authors.initials: G
authors.lastname: Duchesne
authors.forename: Tom
authors.initials: T
authors.lastname: Pickles
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000726:Androgen Antagonists / Q000627:therapeutic use*; D017024:Chemotherapy, Adjuvant / Q000379:methods; D016001:Confidence Intervals; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
chemical_list: D000726:Androgen Antagonists; D017430:Prostate-Specific Antigen