Dosimetric comparison of RapidPlan and manually optimized plans in volumetric modulated arc therapy for prostate cancer

Purpose: This study evaluated whether RapidPlan based plans (RP plans) created by a single optimization, are usable in volumetric modulated arc therapy (VMAT) for patients with prostate cancer. Methods: We used 51 previously administered VMAT plans to train a RP model. Thirty RP plans were created by a single optimization without planner intervention during optimization. Differences between RP plans and clinical manual optimization (CMO) plans created by an experienced planner for the same patients were analyzed (Wilcoxon tests) in terms of homogeneity index (HI), conformation number (CN), D-95%, and D-2% to planning target volume (PTV), mean dose, V-50Gy, V-70Gy, V-75Gy, and V-78Gy to rectum and bladder, monitor unit (MU), and multi-leaf collimator (MLC) sequence complexity. Results: RP and CMO values for PTV D-95%, PTV D-2%, HI, and CN were significantly similar (p < 0.05 for all). RP mean dose, V-50Gy, and V-70Gy to rectum were superior or comparable to CMO values; RP V-75Gy and V-78Gy were higher than in CMO plans (p < 0.05). RP bladder dose-volume parameter values (except V-78Gy) were lower than in CMO plans (p < 0.05). MU values were RP: 730 +/- 55 MU and CMO: 580 +/- 37 MU (p < 0.05); and MLC sequence complexity scores were RP: 0.25 +/- 0.02 and CMO: 0.35 +/- 0.03 (p < 0.05). Conclusions: RP plans created by a single optimization were clinically acceptable in VMAT for patient with prostate cancer. Our simple model could reduce optimization time, independently of planner's skill and knowledge. (C) 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.