title: Later outcomes and alpha/beta estimate from hypofractionated conformal three-dimensional radiotherapy versus standard fractionation for localized prostate cancer.
abstract: OBJECTIVE
  Now that the follow-up time has exceeded 5 years, an estimate of the α/β ratio can be presented. The additional late outcomes in patients treated with three-dimensional conformal external beam radiotherapy for localized prostate cancer using a hypofractionated vs. a standard fractionation regimen are reported from this prospective nonrandomized contemporary comparison.
  
  
  METHODS
  A total of 114 nonrandomized patients chose hypofractionation delivered in 20 fractions of 3 Gy or 3.15 Gy (mean 3.06 Gy) for localized prostate cancer within a median overall time of 32 days (range, 29-49) using four fractions weekly. A total of 160 comparable patients were contemporarily treated within a median of 55 days (range 49-66). The median follow-up was 66 months (range, 24-95) for the hypofractionated arm and 63 months (range, 36-92) for the standard arm. The percentage of patients in the low-, medium-, and high-risk groups was 36%, 46%, and 18% in the hypofractionated arm and 44%, 50%, and 6% in standard arm (2 Gy), respectively.
  
  
  RESULTS
  The 5-year actuarial biochemical absence of disease (prostate-specific antigen nadir + 2 ng/mL) and disease-free survival rate was the same at 89% in both arms, making the α/β calculation unambiguous. The point ratio of α/β was 1.86 (95% confidence interval, 0.7-5.1 Gy). The 95% confidence interval was determined entirely by the binomial confidence limits in the numbers of patients. Rectal reactions of grade 3 and 4 occurred in 1 of 114 (hypofractionated) and 2 of 160 (standard) patients.
  
  
  CONCLUSIONS
  The presented three-dimensional conformal regimen was acceptable, and the α/β value was 1.8, in agreement with other very recent low meta-analyses (reviewed in the "Discussion" section).
authors.affiliation: Department of Radiation Oncology, Hospital Italiano, Montevideo, Uruguay.
authors.forename: Felix
authors.initials: F
authors.lastname: Leborgne
authors.forename: Jack
authors.initials: J
authors.lastname: Fowler
authors.forename: José H
authors.initials: JH
authors.lastname: Leborgne
authors.forename: Julieta
authors.initials: J
authors.lastname: Mezzera
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D019583:Dose Fractionation, Radiation; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000473:pathology; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D015996:Survival Rate; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen