Program Information
Improved Knowledge-Based Bladder and Rectum Dose-Volume Predictions Using a Database of Pareto Optimal Plans in VMAT Planning for Prostate Cancer
P Wall1*, R Carver1,2, and J Fontenot1,2, (1) Louisiana State University, Baton Rouge, LA, (2) Mary Bird Perkins Cancer Center, Baton Rouge, LA
Presentations
TH-EF-FS1-8 (Thursday, August 3, 2017) 1:00 PM - 3:00 PM Room: Four Seasons 1
Purpose: Investigate dose-volume prediction improvements in a common knowledge-based planning (KBP) method using a Pareto optimal plan database compared with a conventional, clinical plan database.
Methods: Two anonymized plan databases were created using the retrospective data of 124 VMAT prostate cancer patients. The clinical plan database (CPD) contained planning data from each patient’s clinically-treated VMAT plan, which were manually optimized by various planners. The multi-criteria optimization database (MCOD) contained Pareto optimal plan data from VMAT plans created using a standardized multi-criteria optimization protocol. Overlap volume histograms, incorporating fractional OAR volumes only within the treatment fields, were computed for each patient and used to match new patient anatomy to similar database patients. For each database patient, CPD and MCOD KBP predictions were generated for D₁₀, D₃₀, D₅₀, D₆₅, and D₈₀ of the bladder and rectum in a leave-one-out manner. Prediction achievability was evaluated through a re-planning study on a subset of 31 random database patients using the most optimal KBP predictions, regardless of plan database origin, as planning goals.
Results: MCOD predictions were significantly lower than CPD predictions for all five bladder dose-volumes and rectum D₅₀ (p = 0.004) and D₆₅ (p < 0.001), while CPD predictions for rectum D₁₀ (p = 0.005) and D₃₀ (p < 0.001) were significantly less than MCOD predictions. KBP predictions were statistically equivalent to re-planned values for all predicted dose-volumes, excluding D₁₀ of bladder (p = 0.03) and rectum (p = 0.04). Compared to clinical plans, re-plans showed significant average reductions in D_mean for bladder (7.8 Gy; p < 0.001) and rectum (9.4 Gy; p < 0.001), while maintaining statistically similar PTV, femoral head, and penile bulb dose.
Conclusion: KBP dose-volume predictions derived from Pareto optimal plans were more optimal overall than those resulting from manually optimized clinical plans, which significantly improved KBP-assisted plan quality.
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