title: An MRI-based dose--reponse analysis of urinary sphincter dose and urinary morbidity after brachytherapy for prostate cancer in a phase II prospective trial.
abstract: OBJECTIVE
  To compare dose-volume histogram variables for the internal and external urinary sphincters (IUS/EUS) with urinary quality of life after prostate brachytherapy.
  
  
  METHODS
  Subjects were 42 consecutive men from a prospective study of brachytherapy as monotherapy with (125)I for intermediate-risk localized prostate cancer. No patient received hormonal therapy. Preplanning constraints included prostate V100 higher than 95%, V150 lower than 60%, and V200 lower than 20% and rectal R100 less than 1cm(3). Patients completed the Expanded Prostate Cancer Index Composite quality-of-life questionnaire before and at 1, 4, 8, and 12 months after implantation, and urinary domain scores were analyzed. All structures including the IUS and EUS were contoured on T2-weighted MRI at day 30, and doses received were calculated from identification of seeds on CT. Spearman's (nonparametric) rank correlation coefficient (ρ) was used for statistical analyses.
  
  
  RESULTS
  Overall urinary morbidity was worst at 1 month after the implant. Urinary function declined when the IUS V285 was 0.4% (ρ=-0.32, p=0.04); bother worsened when the IUS V35 was 99% (ρ=-0.31, p=0.05) or the EUS V240 was 63% (ρ=-0.31, p=0.05); irritation increased when the IUS V35 was 95% (ρ=-0.37, p=0.02) and the EUS V265 was 24% (ρ=-0.32, p=0.04); and urgency worsened when the IUS V35 was 99.5% (ρ=-0.38, p=0.02). Incontinence did not correlate with EUS or IUS dose.
  
  
  CONCLUSIONS
  Doses to the IUS and EUS on MRI/CT predicted worse urinary function, with greater bother, irritative symptoms, and urgency. Incorporating MRI-based dose-volume histogram analysis into the treatment planning process may reduce acute urinary morbidity after brachytherapy.
authors: Department of Radiation Oncology, University of Miami Sylvester Comprehensive Cancer Center, Miami, FL, USA.
authors: Steven P
authors: SP
authors: Register
authors: Rajat J
authors: RJ
authors: Kudchadker
authors: Lawrence B
authors: LB
authors: Levy
authors: David A
authors: DA
authors: Swanson
authors: Thomas J
authors: TJ
authors: Pugh
authors: Teresa L
authors: TL
authors: Bruno
authors: Steven J
authors: SJ
authors: Frank
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D005500:Follow-Up Studies; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000150:complications / Q000175:diagnosis / Q000532:radiotherapy*; D011788:Quality of Life; D011879:Radiotherapy Dosage; D011795:Surveys and Questionnaires; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000503:physiopathology / Q000528:radiation effects*; D014554:Urination / Q000528:radiation effects*; D014555:Urination Disorders / Q000209:etiology / Q000503:physiopathology*