We investigated the application of a differential target- and dose prescription concept for low-dose-rate prostate brachytherapy (LDR-BT), involving a re-distribution of dose according to risk of local failure and treatment-related morbidity.
Our study included 15 patients. Multi-parametric MRI was acquired prior to LDR-BT for gross tumor volume (GTV) delineation. Trans-rectal ultrasound (US) images were acquired during LDR-BT for prostate gland- (CTVProstate) and organs at risk delineation. The GTV contour was transferred to US images after US/MRI registration. An intermediate-risk target volume (CTVProstate) and a high-risk target volume (CTVHR=GTV+5mm margin) were defined. Two virtual dose plans were made: Planrisk-adapt consisted of a de-escalated dose of minimum 125Gy to the CTVProstate and an escalated dose to 145-250Gy to the CTVHR; Planref included the standard clinical dose of minimum 145Gy to the CTVProstate. Dose-volume-histogram (DVH) parameters were expressed in equivalent 2Gy fractionation doses.
The median D90% to the GTV and CTVHR significantly increased by 44Gy and 17Gy, respectively when comparing Planrisk-adapt to Planref. The median D10% and D30% to the urethra significantly decreased by 9Gy and 11Gy, respectively and for bladder neck by 18Gy and 15Gy, respectively. The median rectal D2. 0cm(3) had a significant decrease of4Gy, while the median rectal D0. 1cm(3) showed an increase of 1Gy.
Our risk adaptive target- and dose prescription concept of prescribing a lower dose to the whole gland and an escalated dose to the GTV using LDR-BT seed planning was technically feasible and resulted in a significant dose-reduction to urethra and bladder neck.
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2015 Jun 16 [Epub]
Susanne Rylander, Daniel Polders, Marcel J Steggerda, Luc M Moonen, Kari Tanderup, Uulke A Van der Heide
Institute of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Medical Physics, Aarhus University Hospital, Aarhus, Denmark. Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands. , Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands. , Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands. , Institute of Clinical Medicine, Aarhus University Hospital, Aarhus, Denmark; Department of Oncology, Aarhus University Hospital, Aarhus, Denmark. , Department of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.