title: Patient-assessed late toxicity rates and principal component analysis after image-guided radiation therapy for prostate cancer.
abstract: OBJECTIVE
  The aims of this study were to determine the incidence of patient-assessed late toxicity after high-dose, image-guided radiation therapy in a cohort of men with prostate cancer; and to correlate toxicity with conventional dosimetric parameters and rectal and bladder dose-volume histograms (DVH) reduced using principal component analysis.
  
  
  METHODS
  Toxicity questionnaires were sent to 690 men treated for localized prostate cancer to 75.6 Gy or 79.8 Gy using three-dimensional conformal radiation therapy (3DCRT) or intensity-modulated radiation therapy (IMRT) between 1997 and 2003 at the Princess Margaret Hospital. Toxicity was graded according to the modified Radiation Therapy Oncology Group (RTOG)-late effects normal tissue (LENT) scoring system. Late rectal and bladder toxicity scores were dichotomized as < Grade 2 and > or = Grade 2, and correlated with dosimetric parameters and with the first three principal components of rectal and bladder DVHs.
  
  
  RESULTS
  In all, 63% of the patients completed the questionnaire. At a median follow-up of 37 months, the incidence of late rectal toxicity RTOG Grades 1, 2, and 3 was 25.2%, 2.5%, and 0.7% respectively. The incidence of late urinary toxicity RTOG Grade 1, 2, and 3 was 16.5%, 8.8%, and 0.9% respectively. Maintenance of erectile function sufficient for intercourse was reported in 68%. No dosimetric parameter analyzed, including principal component analysis reduction of DVHs, correlated with late toxicity.
  
  
  CONCLUSIONS
  Postal questionnaire was effective for collection of patient-assessed late toxicity data. The incidence of late toxicity was low, with a lack of correlation to dosimetric parameters. We attribute this to the use of conformal techniques and daily image guidance.
authors: Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, ON, Canada.
authors: Marketa
authors: M
authors: Skala
authors: Tara
authors: T
authors: Rosewall
authors: Laura
authors: L
authors: Dawson
authors: Lorella
authors: L
authors: Divanbeigi
authors: Gina
authors: G
authors: Lockwood
authors: Christopher
authors: C
authors: Thomas
authors: Juanita
authors: J
authors: Crook
authors: Peter
authors: P
authors: Chung
authors: Padraig
authors: P
authors: Warde
authors: Charles
authors: C
authors: Catton
mesh_terms: D003952:Diagnostic Imaging / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008297:Male; D009864:Ontario / Q000453:epidemiology; D025341:Principal Component Analysis; D011471:Prostatic Neoplasms / Q000175:diagnosis / Q000453:epidemiology* / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000453:epidemiology*; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted / Q000706:statistics & numerical data*; D020266:Radiotherapy, Conformal / Q000706:statistics & numerical data*; D012002:Rectal Diseases / Q000453:epidemiology*; D012189:Retrospective Studies; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D011795:Surveys and Questionnaires; D001745:Urinary Bladder Diseases / Q000453:epidemiology*