Author: Alyssa Gadsby, William J. Godwin, Daniel G. McDonald, Jean L. Peng, Alek K. Rapchak, Sean A Roles, Austin M. Skinner, Stephanie Tan 👨🔬
Affiliation: Medical University of South Carolina 🌍
Purpose: To utilize multi-criteria optimization (MCO) in a targeted fashion to quickly and easily improve dose to the rectum when treating the prostate with stereotactic body radiation therapy (SBRT).
Methods: Ten anonymized prostate SBRT datasets were utilized. Clinically approved VMAT treatment plans, optimized using standard optimization (SO) by a skilled dosimetrist, and planned with the Eclipse v16.1 treatment planning system, served as baseline. MCO Pareto plans were then generated from SO baseline for each case. Only the rectum was selected, and all rectum objectives, previously used during SO, were combined during Pareto generation. The MCO slider for the rectum was positioned at mid-point for improvement, and a final plan was generated. Total time from MCO start was recorded. SO and MCO plans were normalized to provide 95% PTV coverage of the prescription dose (40Gy in five fractions). SO structure doses were compared to MCO. Structures included: Bladder, Bladder Wall, Rectum, Rectal Wall, Femurs, Urethra, Penile Bulb and Pudendal Arteries. Student’s T-test was used to assess significance.
Results: Final MCO plans were generated within 15 minutes for all patients. Rectum and rectal wall showed decreases on average for all metrics evaluated. Rectum D3cc, D10%, and D20% decreased significantly by 8.6±4.5%, 10.4±4.2%, 11.3±5.2%, on average, respectively. Rectal wall D1cc and D53% also decreased significantly by 8.1±5.1% and 13.8±6.8%, respectively. Femurs showed a mild increase in dose for MCO, with D1cc increasing with significance by 2.8±0.9%. Remaining structures showed no significant change in dose. Bladder D0.03cc and D50% showed an average change of -0.1±1.7% and -0.7±2.4%, respectively.
Conclusion: MCO can rapidly reduce dose to a single structure, following SO, for complex cases like prostate SBRT. MCO functionality, used in a targeted fashion, provides significant reduction in dose for select structures, and requires minimal computation time, allowing for effective utilization in the busy clinic.