title: Dosimetric feasibility of ablative dose escalated focal monotherapy with MRI-guided high-dose-rate (HDR) brachytherapy for prostate cancer.
abstract: To determine the dosimetric feasibility of dose-escalated MRI-guided high-dose-rate brachytherapy (HDR-BT) focal monotherapy for prostate cancer (PCa).
  
  
  
  In all patients, GTV was defined with mpMRI, and deformably registered onto post-catheter insertion planning MRI. PTV included the GTV plus 9mm craniocaudal and 5mm in every other direction. In discovery-cohort, plans were obtained for each PTV independently aiming to deliver ⩾16.5Gy/fraction (two fraction schedule) while respecting predefined organs-at-risk (OAR) constraints or halted when achieved equivalent single-dose plan (24Gy). Dosimetric results of original and focal HDR-BT plans were evaluated to develop a planning protocol for the validation-cohort.
  
  
  
  In discovery-cohort (20-patients, 32-GTVs): PTV D95% ⩾16.5Gy could not be reached in a single plan (3%) and was accomplished (range 16.5-23.8Gy) in 15 GTVs (47%). Single-dose schedule was feasible in 16 (50%) plans. In the validation-cohort (10-patients, 10-GTVs, two separate implants each): plans met acceptable and ideal criteria in 100% and 43-100% respectively. Migration to single-dose treatment schedule was feasible in 7 implants (35%), without relaxing OAR's constraints or increasing the dose (D100% and D35%) to mpMRI-normal prostate (p>0.05).
  
  
  
  Focal ablative dose-escalated radiation is feasible with the proposed protocol. Prospective studies are warranted to determine the clinical outcomes.
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre - University Health Network, Department of Radiation Oncology, University of Toronto, Canada.
authors.forename: Ali
authors.initials: A
authors.lastname: Hosni
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre - University Health Network, Department of Radiation Oncology, University of Toronto, Canada.
authors.forename: Marco
authors.initials: M
authors.lastname: Carlone
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre - University Health Network, Department of Radiation Oncology, University of Toronto, Canada.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Rink
authors.affiliation: Département de radio-oncologie, Centre hospitalier de l'Université de Montréal (CHUM), Montréal, Canada.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Ménard
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre - University Health Network, Department of Radiation Oncology, University of Toronto, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Chung
authors.affiliation: Radiation Medicine Program, Princess Margaret Cancer Centre - University Health Network, Department of Radiation Oncology, University of Toronto, Canada. Electronic address: alejandro.berlin@rmp.uhn.ca.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Berlin
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D058958:Organs at Risk; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011874:Radiometry; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided / Q000379:methods*
keywords: Focal therapy; HDR brachytherapy; MRI; Prostate cancer