title: Long-term outcome of magnetic resonance spectroscopic image-directed dose escalation for prostate brachytherapy.
abstract: To report the long-term control and toxicity outcomes of patients with clinically localized prostate cancer, who underwent low-dose-rate prostate brachytherapy with magnetic resonance spectroscopic image (MRSI)-directed dose escalation to intraprostatic regions.
  
  
  
  Forty-seven consecutive patients between May 2000 and December 2003 were analyzed retrospectively. Each patient underwent a preprocedural MRSI, and MRS-positive voxels suspicious for malignancy were identified. Intraoperative planning was used to determine the optimal seed distribution to deliver a standard prescription dose to the entire prostate, while escalating the dose to MRS-positive voxels to 150% of prescription. Each patient underwent transperineal implantation of radioactive seeds followed by same-day CT for postimplant dosimetry.
  
  
  
  The median prostate D90 (minimum dose received by 90% of the prostate) was 125.7% (interquartile range [IQR], 110.3-136.5%) of prescription. The median value for the MRS-positive mean dose was 229.9% (IQR, 200.0-251.9%). Median urethra D30 and rectal D30 values were 142.2% (137.5-168.2%) and 56.1% (40.1-63.4%), respectively. Median followup was 86.4 months (IQR, 49.8-117.6). The 10-year actuarial prostate-specific antigen relapse-free survival was 98% (95% confidence interval, 93-100%). Five patients (11%) experienced late Grade 3 urinary toxicity (e.g., urethral stricture), which improved after operative intervention. Four of these patients had dose-escalated voxels less than 1.0 cm from the urethra.
  
  
  
  Low-dose-rate brachytherapy with MRSI-directed dose escalation to suspicious intraprostatic regions exhibits excellent long-term biochemical control. Patients with dose-escalated voxels close to the urethra were at higher risk of late urinary stricture.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Martin T
authors.initials: MT
authors.lastname: King
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Nasser
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Nitin
authors.initials: N
authors.lastname: Mathur
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Gil'ad N
authors.initials: GN
authors.lastname: Cohen
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Marisa A
authors.initials: MA
authors.lastname: Kollmeier
authors.affiliation: Department of Radiation Oncology, The Carlo Fidani Regional Cancer Centre, Mississauga, Ontario.
authors.forename: Jasper
authors.initials: J
authors.lastname: Yuen
authors.affiliation: Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Hebert A
authors.initials: HA
authors.lastname: Vargas
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Xin
authors.initials: X
authors.lastname: Pei
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Yamada
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Kristen L
authors.initials: KL
authors.lastname: Zakian
authors.affiliation: Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY.
authors.forename: Marco
authors.initials: M
authors.lastname: Zaider
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY. Electronic address: zelefskm@mskcc.org.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zelefsky
mesh_terms: D000368:Aged; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D018572:Disease-Free Survival; D005500:Follow-Up Studies; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology; D011879:Radiotherapy Dosage; D012007:Rectum / Q000528:radiation effects; D012189:Retrospective Studies; D013997:Time Factors; D014521:Urethra / Q000528:radiation effects; D014525:Urethral Stricture / Q000209:etiology
chemical_list: D017430:Prostate-Specific Antigen
keywords: Brachytherapy; Dose escalation; MR spectroscopy; Prostate