Inclusion of radiobiological factors in prostate brachytherapy treatment planning

Abstract

AbstractPurpose: Comparison of prostate seed implant treatment plans is currently based on evaluation of dose-volume histograms and doses to the tumour and normal structures. However, these do not account for effects of varying dose-rate, tumour repopulation and other biological effects. In this work, incorporation of the radiobiological response is used to obtain a more inclusive and clinically relevant treatment plan evaluation tool.Materials and Methods: Ten patients were evaluated. For each patient, six different treatment plans were created on the Prowess system. Plans with iodine-125 used a prescription dose of 145 Gy while plans with palladium-103 used 115 Gy. The biologically effective dose was used together with the tumour control probability and the normal tissue complication probabilities of urethra, bladder, rectum and surrounding tissue to evaluate the effectiveness of each treatment plan. Results from the radiobiological evaluation were compared to standard dose quantifiers.Results: The use of response probabilities is seen to provide a simpler means of treatment evaluation compared to standard dose quantifiers. This allows for different treatment plans to be quickly compared. Additionally, the use of radiobiologically-based plan evaluation allows for optimisation of seed type and initial seed strengths to find the ideal balance of TCP and NTCP.Conclusion: The goal of this work was to incorporate the biological response to obtain a more complete and clinically relevant treatment plan evaluation tool. This resulted in a simpler means of plan evaluation that may be used to compare and optimise prostate seed implant treatment plans.