Various cost functions evaluation of commercial biologically based treatment planning system for nasopharyngeal cancer.

The aim of this study was to evaluate various combinations of Equivalent Uniform Dose (EUD) based and Dose Volume based (DV) cost functions in terms of target coverage and organ sparing for Nasopharyngeal CA. Ten patients diagnosed with Nasopharyngeal CA were selected for this retrospective study. Different hybrid VMAT plans, including EUD- and DV-based cost functions, were generated for each patient to determine the optimum combination in terms of organ sparing and target coverage. The generated VMAT plans were evaluated based on physical and biological dose parameters. No statistical difference was observed among all plans in terms of target coverage. The p values were >/= 0.005 for V95, D(mean), and tumor control probability (TCP). The MU efficiency was maximum (67%), and the number of segments (285 segments) was minimum in Hybrid plan. Hybrid plan showed a significant difference compared to others (p = 0.001) in terms of serial organs. Moreover, the combination of serial and parallel complication models provided better reduction of radiation dose in the parotid glands in Plan-3 (p = 0.001). In this study, better protection was obtained when DVH-based cost functions were defined for targets and a combination of EUD- and DVH-based cost functions were used for OARs.