Prostate cancer focal brachytherapy: Improving treatment plan robustness using a convolved dose rate model

Low-risk prostate cancer can be treated by focal brachytherapy, in which small radioactive seeds are implanted directly into the prostate at targeted locactions. Treatment planning is complicated by post-operative displacement of the seeds from their intended location. This reduces the actual dose received by the prostate and increases the dose to surrounding tissue such as the urethra and rectum, potentially causing harmful side-effects. Current treatment planning methods do not explicitly incorporate the effect of post-operative seed displacement. To address this, the radiation dose rate function used during planning is modified to reflect displacement using convolution. This new dose rate model enables plans to be produced automatically and efficiently. Simulation experiments show that treatment plans made using the convolved dose rate function are more robust to seed displacement than those using the original unconvolved dose, preserving treatment efficacy but giving increased protection to surrounding tissue. (C) 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the International Conference on Computational Science