Program Information
A Stochastic Frontier Analysis for Enhanced Quality Control of High-Dose-Rate Brachytherapy Treatment Plans
P Edimo1,2*, L Archambault1,2 , L Beaulieu1,2 , (1) Departement de Physique, de Genie Physique et d'Optique, Universite Laval, 2325 Rue de l'Universite, Quebec (QC), G1V 0A6, Canada. (2) Departement de Radio-Oncologie et Centre de Recherche en Cancerologie, CHU de Quebec, 11 Cote du Palais, Quebec (QC), G1R 2J6, Canada.
Presentations
SU-K-FS2-6 (Sunday, July 30, 2017) 4:00 PM - 6:00 PM Room: Four Seasons 2
Purpose: To introduce a quality control model of High-Dose-Rate brachytherapy plans, based on patient-specific geometric parameters, using the stochastic frontier analysis; a method of economic modeling. The goal of the model is to predict how much dose can be reduced to organ at risk (OAR), while maintaining or increasing the target volume coverage. The planner technical inefficiency (TI) is furthermore possible to be quantify from this model.
Methods: A sample of 500 HDR boost plans for prostate cancer have been selected. The dose optimization is performed with Inverse Planning Simulated Annealing (IPSA) algorithm in the Oncentra treatment planning system (Elekta – Brachy, Veneedal, The Netherlands). The geometric parameters involved in the model are the target volume, the OARs volume and the Hausdorff distance between PTV and OARs. A stochastic frontier model (SFM) has been built from the Cobb–Douglas function for each organ: production frontier for the PTV and cost frontier for OARs.
Results: Results show TI for the PTV, bladder and urethra. V₇₅ for the bladder can be decreased up to 1.57cc for 77% of patients. IPSA computed values for the bladder range from 0.004-1.967cc and SFM from 0.019-0.696cc. Furthermore, the target volume coverage, V₁₀₀, can be increased up to 6.86% of the IPSA computed values for 87% of patients. No technical inefficiency was observed for the rectum. The TI for the PTV coverage range from 0.23 to 5.23, indicating that a significant improvement of PTV coverage is possible for most patients without compromising OARs sparing.
Conclusion: The current results indicate stochastic frontier analysis identify potential sparing of OARs and the increase of the PTV coverage for 87% of plans. Of those, 8% were identified to be highly inefficient (low PTV coverage). This demonstrates that IPSA clinical acceptable plans are not necessarily the best that can be achieved.
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