title: A radiobiology-based inverse treatment planning method for optimisation of permanent l-125 prostate implants in focal brachytherapy.
abstract: Treatment plans for ten patients, initially treated with a conventional approach to low dose-rate brachytherapy (LDR, 145 Gy to entire prostate), were compared with plans for the same patients created with an inverse-optimisation planning process utilising a biologically-based objective. The 'biological optimisation' considered a non-uniform distribution of tumour cell density through the prostate based on known and expected locations of the tumour. Using dose planning-objectives derived from our previous biological-model validation study, the volume of the urethra receiving 125% of the conventional prescription (145 Gy) was reduced from a median value of 64% to less than 8% whilst maintaining high values of TCP. On average, the number of planned seeds was reduced from 85 to less than 75. The robustness of plans to random seed displacements needs to be carefully considered when using contemporary seed placement techniques. We conclude that an inverse planning approach to LDR treatments, based on a biological objective, has the potential to maintain high rates of tumour control whilst minimising dose to healthy tissue. In future, the radiobiological model will be informed using multi-parametric MRI to provide a personalised medicine approach.
authors.affiliation: Department Physical Sciences Peter MacCallum Cancer Centre, Vic, 3002, Australia. Sir Peter MacCallum Department of Oncology, University of Melbourne, Vic, 3010, Australia.
authors.forename: Annette
authors.initials: A
authors.lastname: Haworth
authors.forename: Christopher
authors.initials: C
authors.lastname: Mears
authors.forename: John M
authors.initials: JM
authors.lastname: Betts
authors.forename: Hayley M
authors.initials: HM
authors.lastname: Reynolds
authors.forename: Guido
authors.initials: G
authors.lastname: Tack
authors.forename: Kevin
authors.initials: K
authors.lastname: Leo
authors.forename: Scott
authors.initials: S
authors.lastname: Williams
authors.forename: Martin A
authors.initials: MA
authors.lastname: Ebert
mesh_terms: D001918:Brachytherapy / Q000379:methods*; D054855:Drug-Eluting Stents; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage / Q000627:therapeutic use*; D008297:Male; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011836:Radiation Tolerance; D019275:Radiopharmaceuticals / Q000008:administration & dosage / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014521:Urethra / Q000528:radiation effects
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals