Multivariable normal tissue complication probability model-based treatment plan optimization for grade 2-4 dysphagia and tube feeding dependence in head and neck radiotherapy.

Background And Purpose: Radiotherapy of the head and neck is challenged by the relatively large number of organs-at-risk close to the tumor. Biologically-oriented objective functions (OF) could optimally distribute the dose among the organs-at-risk. We aimed to explore OFs based on multivariable normal tissue complication probability (NTCP) models for grade 2-4 dysphagia (DYS) and tube feeding dependence (TFD).

Materials And Methods: One hundred head and neck cancer patients were studied. Additional to the clinical plan, two more plans (an OF and OF-plan) were optimized per patient. The NTCP models included up to four dose-volume parameters and other non-dosimetric factors. A fully automatic plan optimization framework was used to optimize the OF-based plans.

Results: All OF-based plans were reviewed and classified as clinically acceptable. On average, the Δdose and ΔNTCP were small comparing the OF-plan, OF-plan, and clinical plan. For 5% of patients NTCP reduced >5% using OF-based planning compared to the OF-plans.

Conclusions: Plan optimization using NTCP- and NTCP-based objective functions resulted in clinically acceptable plans. For patients with considerable risk factors of TFD, the OF steered the optimizer to dose distributions which directly led to slightly lower predicted NTCP values as compared to the other studied plans.