title: Improved clinical outcomes with high-dose image guided radiotherapy compared with non-IGRT for the treatment of clinically localized prostate cancer.
abstract: OBJECTIVE
  To compare toxicity profiles and biochemical tumor control outcomes between patients treated with high-dose image-guided radiotherapy (IGRT) and high-dose intensity-modulated radiotherapy (IMRT) for clinically localized prostate cancer.
  
  
  METHODS
  Between 2008 and 2009, 186 patients with prostate cancer were treated with IGRT to a dose of 86.4 Gy with daily correction of the target position based on kilovoltage imaging of implanted prostatic fiducial markers. This group of patients was retrospectively compared with a similar cohort of 190 patients who were treated between 2006 and 2007 with IMRT to the same prescription dose without, however, implanted fiducial markers in place (non-IGRT). The median follow-up time was 2.8 years (range, 2-6 years).
  
  
  RESULTS
  A significant reduction in late urinary toxicity was observed for IGRT patients compared with the non-IGRT patients. The 3-year likelihood of grade 2 and higher urinary toxicity for the IGRT and non-IGRT cohorts were 10.4% and 20.0%, respectively (p = 0.02). Multivariate analysis identifying predictors for grade 2 or higher late urinary toxicity demonstrated that, in addition to the baseline Internatinoal Prostate Symptom Score, IGRT was associated with significantly less late urinary toxicity compared with non-IGRT. The incidence of grade 2 and higher rectal toxicity was low for both treatment groups (1.0% and 1.6%, respectively; p = 0.81). No differences in prostate-specific antigen relapse-free survival outcomes were observed for low- and intermediate-risk patients when treated with IGRT and non-IGRT. For high-risk patients, a significant improvement was observed at 3 years for patients treated with IGRT compared with non-IGRT.
  
  
  CONCLUSIONS
  IGRT is associated with an improvement in biochemical tumor control among high-risk patients and a lower rate of late urinary toxicity compared with high-dose IMRT. These data suggest that, for definitive radiotherapy, the placement of fiducial markers and daily tracking of target positioning may represent the preferred mode of external-beam radiotherapy delivery for the treatment of prostate cancer.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. Zelefskm@mskcc.org
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zelefsky
authors.forename: Marisa
authors.initials: M
authors.lastname: Kollmeier
authors.forename: Brett
authors.initials: B
authors.lastname: Cox
authors.forename: Anthony
authors.initials: A
authors.lastname: Fidaleo
authors.forename: Dahlia
authors.initials: D
authors.lastname: Sperling
authors.forename: Xin
authors.initials: X
authors.lastname: Pei
authors.forename: Brett
authors.initials: B
authors.lastname: Carver
authors.forename: Jonathan
authors.initials: J
authors.lastname: Coleman
authors.forename: Michael
authors.initials: M
authors.lastname: Lovelock
authors.forename: Margie
authors.initials: M
authors.lastname: Hunt
mesh_terms: D000368:Aged; D057918:Fiducial Markers; D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000473:pathology / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000517:prevention & control; D011879:Radiotherapy Dosage; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D012189:Retrospective Studies; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000528:radiation effects
chemical_list: D017430:Prostate-Specific Antigen