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Title: Dosimetry Modeling for Focal Low-Dose-Rate Prostate Brachytherapy

Purpose: Focal brachytherapy targeted to an individual lesion(s) within the prostate may reduce side effects experienced with whole-gland brachytherapy. The outcomes of a consensus meeting on focal prostate brachytherapy were used to investigate optimal dosimetry of focal low-dose-rate (LDR) prostate brachytherapy targeted using multiparametric magnetic resonance imaging (mp-MRI) and transperineal template prostate mapping (TPM) biopsy, including the effects of random and systematic seed displacements and interseed attenuation (ISA). Methods and Materials: Nine patients were selected according to clinical characteristics and concordance of TPM and mp-MRI. Retrospectively, 3 treatment plans were analyzed for each case: whole-gland (WG), hemi-gland (hemi), and ultra-focal (UF) plans, with 145-Gy prescription dose and identical dose constraints for each plan. Plan robustness to seed displacement and ISA were assessed using Monte Carlo simulations. Results: WG plans used a mean 28 needles and 81 seeds, hemi plans used 17 needles and 56 seeds, and UF plans used 12 needles and 25 seeds. Mean D90 (minimum dose received by 90% of the target) and V100 (percentage of the target that receives 100% dose) values were 181.3 Gy and 99.8% for the prostate in WG plans, 195.7 Gy and 97.8% for the hemi-prostate in hemi plans, and 218.3 Gy and 99.8% for themore » focal target in UF plans. Mean urethra D10 was 205.9 Gy, 191.4 Gy, and 92.4 Gy in WG, hemi, and UF plans, respectively. Mean rectum D2 cm{sup 3} was 107.5 Gy, 77.0 Gy, and 42.7 Gy in WG, hemi, and UF plans, respectively. Focal plans were more sensitive to seed displacement errors: random shifts with a standard deviation of 4 mm reduced mean target D90 by 14.0%, 20.5%, and 32.0% for WG, hemi, and UF plans, respectively. ISA has a similar impact on dose-volume histogram parameters for all plan types. Conclusions: Treatment planning for focal LDR brachytherapy is feasible. Dose constraints are easily met with a notable reduction to organs at risk. Treating smaller targets makes seed positioning more critical.« less
Authors:
 [1] ;  [1] ; ;  [1] ;  [2] ;  [3] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Leeds Cancer Centre, Leeds Teaching Hospitals NHS Trust, Leeds (United Kingdom)
  2. Division of Surgery and Interventional Science, University College London, London (United Kingdom)
  3. (United Kingdom)
  4. University College London Hospital, London (United Kingdom)
  5. St Luke's Cancer Centre, Guildford (United Kingdom)
Publication Date:
OSTI Identifier:
22462373
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 92; Journal Issue: 4; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BIOPSY; BRACHYTHERAPY; COMPUTERIZED SIMULATION; DOSE RATES; DOSIMETRY; HAZARDS; LIMITING VALUES; MONTE CARLO METHOD; NMR IMAGING; PATIENTS; PLANNING; POSITIONING; PROSTATE; RADIATION DOSES; RADIATION SOURCE IMPLANTS; RECTUM; SIDE EFFECTS; URINARY TRACT