Room: Karl Dean Ballroom A1
Purpose: Recently we developed and validated automated multi-criteria treatment planning for 4x9.5 Gy HDR prostate monotherapy. Generated plans were Pareto-optimal and demonstrated consistent reduction in urethra dose, the most dose limiting organ-at-risk, compared to clinical planning. Single fraction HDR monotherapy for prostate cancer requires dose escalation under tight constraints for the organs-at-risk, ideally obtained by on-line treatment planning. We investigated the dosimetric feasibility of single fraction HDR monotherapy by comparing our clinical treatment planning system (TPS) workflow to our in-house developed approach for fast, on-line automated treatment planning.
Methods: In this study, we configured automated planning for 20 Gy single fraction. The objective was to maximize target coverage under the following constraints: urethra D0.1cc<21Gy, D10%<20.5Gy; rectum D1cc<15.5Gy, D2cc<14.5Gy; bladder D1cc<16Gy, D2cc<15.5Gy. For 9 patients, automatically generated plans were compared with reference plans based on our clinical workflow, regarding plan quality and optimization time. For automated planning, the structures and implant geometry of each patient were exported from the clinical TPS, followed by dwell time optimization using the novel in-house developed automated treatment planning approach. Subsequently, the dwell times were imported in the clinical TPS for forward dose calculation and comparison with the clinical dose distribution.
Results: For each patient, the target coverage for the automated plan was higher than for the reference plan (mean 97.3% [94.3%-99.0%] versus 94.8% [91.6%-96.6%]), while strictly obeying all hard planning constraints. 8/9 automated plans resulted in target coverage >95% compared to only 5/9 reference plans, while the minimum obtained coverage was 94.3% compared to 91.6%. The mean automated planning time was 1.2 seconds (range 0.8sec-1.9sec). For the reference plans, the planning times were in the range of 5-10 minutes.
Conclusion: Automated treatment planning for prostate HDR brachytherapy is ultra-fast (<2sec) and resulted in high plan quality, enabling on-line treatment planning in dose escalated prostate HDR.