Clinical Evaluation of Generalized Optimization for Reference-Free Direct-to-Unit Prostate Radiation Therapy
Abstract
Purpose
To explore utilization of a generalized planning template to enable reference-free direct-to-unit treatment for prostate cancer.
Methods
Direct-to-unit workflows bypass acquisition of a CTSim, often by using diagnostic imaging. For reference-free treatments, personalization occurs through an adaptive process once the patient arrives for treatment. This necessitates a generalized approach to reference plan generation. Plans for 20 prostate patients (60 Gy/20 fx, 9 or 12 field IMRT) were reviewed for further investigation. A generalized planning template was created using a weighted averaged order of dose goals across all original personalized plans. This class solution was then used to generate a new plan for each patient. These plans were compared for non-inferiority in target coverage and OAR sparing using Wilcoxon signed rank tests. To assess clinical feasibility, reference-free plans were compared to clinical plans by four experts, one dosimetrist and three radiation oncologists, using a structured survey.
Results
No statistically significant differences were found between personalized and generalized plans for PTV, CTV, and nearby OAR metrics. For 95% of cases (n=19), at least half of the expert panel expressed either no preference or a preference for the generated plan over the clinical plan. For 8 out of 20 cases, the entire panel reported no preference or a preference for the generated plan over the established clinical plan.
Conclusion
Statistical analysis found that plans did not differ significantly despite careful optimization and personalization of clinical plans. Detailed review by experienced experts supported these results, indicating no underlying clinical differences. A reference-free procedure could be incorporated into the clinical workflow for straight forward prostate treatment, reducing overall plan preparation and reducing site visits. Further personalization of the plan may be achieved with other ART techniques, such as daily imaging and contouring which is used to adapt plans to changes in daily anatomy.