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Session: Onco
Session starts: Friday 27 January, 11:30
Presentation starts: 12:45
Room: Room 558

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Martijn de Vries ()
Miranda Christianen ()
Lorne Luthart ()
Kim de Vries ()
Inger-Karine Kolkman-Deurloo ()
John van den Dobbelsteen ()

Abstract:
Prostate cancer patients with an enlarged prostate and/or excessive pubic arch interference (PAI) are generally considered non-eligible for treatment with high-dose-rate brachytherapy (HDR BT). Recently, steerable needles have been developed that allow for high targeting accuracy and curved needle trajectories (de Vries et al. PLOS One, 2021). This study validates 1) the ability of these steerable needles to avoid PAI and 2) the feasibility of implanting the steerable needles according to the pre-treatment plan in the clinical setting. HDR BT treatment planning and implantation studies were performed with steerable needles and a prostate phantom with an enlarged prostate (> 55 cm3) and excessive PAI (10 mm). Four pre-treatment plans were generated in the Oncentra® Prostate (OCP) treatment planning system (TPS) (Elekta Instrument AB, Sweden) considering the dosimetric constraints: prostate V100 > 95%, urethra D0.1cm3 < 115% and rectum D1cm3 < 75%. Plan A did not consider PAI functioning as the baseline plan. The other pre-treatment plans considered PAI of which plans B and C only used rigid needles and plan D incorporated rigid and steerable needles to overcome PAI. Dose-volume histogram (DVH) outcomes evaluated the quality of the pre-treatment plans and conformance to these plans after implantation. The DVH values of the steerable needle plan approached upon the outcomes for the baseline plan and increased prostate V100 up to 17.1% compared to the rigid needle plans. The dose to the urethra remained below the dose criteria of 115%. The physician was able to implant the steerable needle plan with the highest conformance to the pre-treatment plan, no major changes in the clinical workflow, and no changes in the clinical set-up. The steerable needle approach allows for more flexibility in needle placement, mitigation of deflections and the avoidance of PAI. The curved trajectories can be easily planned in the OCP TPS and implantation can be performed with excellent agreement between pre-treatment and postimplant plan. An adequate dose distribution can be achieved, and hence, men with enlarged and/or excessive PAI can be considered to be treated with HDR BT.