Evaluating the efficacy of biological versus physical cost functions with constrained mode for inverse plan optimization of head and neck cancer.

This study aims to compare and evaluate the potential benefits of using single DV-based, multiple DV-based physical cost function, and biological-based cost functions for organs at risk (OARs) sparing in IMRT as well as VMAT plans of head and neck cancer. Forty head and neck cancer patients treated with inverse plan optimization techniques were retrospectively enrolled for this study. Three different treatment plans were optimized by single DV-based, multiple DV-based physical cost functions, and biological-based cost functions on MONACO 6.1® TPS. All three optimized plans were normalized to deliver the same prescribed target dose. All 120 optimized plans were analyzed using dose evaluation parameters. For IMRT plans, the biological cost functions (BCF) were superior to both DV-based optimizations when it came to the mean dose of parallel organs. For VMAT plans, multiple DV-based physical cost function optimization resulted in a lower mean dose of parallel organs when compared with other two optimization. The biological cost function significantly reduced the mean dose of parallel organs, for which multiple DV-based cost functions were not used. In both IMRT and VMAT plans, the DV-based physical cost function significantly reduced the maximum dose of serial organs, with the exception of the mandible. Biological-based optimization made it more likely that the parallel OARs would be spared in IMRT plans, while multiple DV-based optimization made it more likely that the parallel OARs would be spared in VMAT plans. Both DV-based optimization in IMRT and VMAT plans effectively spared the maximum dose of the serial organ.