Fast automated multi-criteria planning for HDR brachytherapy explored for prostate cancer

We developed a fast and fully-automated, multi-criteria treatment planning workflow for high dose rate brachytherapy (HDR-BT). In this workflow, the patient-CT with catheter reconstructions and dwell positions are imported from the clinical TPS into a novel system for automated dwell time optimisation. The optimised dwell times are then imported into the clinical TPS. The aims of automation were (1) planner-independent, enhanced plan quality, (2) short optimisation times. Our in-house developed system for fully automated, multi-criteria external beam radiotherapy (EBRT) treatment planning (Erasmus-iCycle) was adapted for optimisation of HDR-BT dose distributions. The investigations were performed with planning CT scans with catheter reconstructions and delineations of twenty-five low- A nd intermediate-risk prostate cancer patients who were previously treated in our center with 4 × 9.5 Gy HDR-BT. Automatically generated plans (autoplans) were compared to the corresponding clinical plans. All evaluations were performed in the clinical TPS. The requested 95% tumour coverage was obtained for all autoplans, while this was only observed in 23/25 clinical plans. All autoplans showed a consistent reduction of the D1% for the highest prioritised OAR, the urethra. The average and maximum reductions were 6.3%-point and 12.1%-point of the prescribed dose, respectively. In addition, conformality of the autoplans was higher. The autoplans had slightly smaller delivery times. Autoplanning took on average 4.6 s, including computation of the dose kernels.