Investigating the Impact of Using TCP and NTCP Informed Objectives In Treatment Plan Optimization of Head & Neck Cancers
Abstract
Purpose
To investigate treatment plan quality of head and neck cancers via tumor control and normal tissue complications probability (TCP and NTCP) objectives in the plan optimization process.
Methods
An oropharyngeal squamous cell carcinoma patient was used to create two sets of treatment plans in in Raystation TPS (2024A). Conventional physical objectives for target coverage and OAR sparing were first used to derive TCP/NTCP and mean dose values which then used to inform objective for the second plan. The Poisson TCP model was used for the targets and the relative seriality NTCP model for the OARs. The models’ parameters that were used were taken from the literature or derived from own clinical data. TCP/NTCP values and doses of the respective plans were compared between the initial dosimetric optimized and radiobiological optimized plan
Results
All high risk and standard risk PTV’s prescription doses satisfied D95% coverage constraint while calculated TCP values were >98% for all PTVs, in both sets of plans. The radiobiological informed plan had increased mean cord dose to 16.07 Gy from 11.35 while maintaining similar NTCP. For the rest of the OARs (brain, parotid and submandibular glands, pharyngeal constrictors, right cochlea, esophagus and oral cavity) the mean dose generally decreased or stay the same. Left Submandibular and parotid gland saw the greatest change in NTCP (-1% and 0.5% respectively) while the rest stayed the same.
Conclusion
Radiobiological NTCP and TCP values were used to inform objectives to further optimize an initial dosimetric optimal plan. Future work will involve using radibiolgical optimization directly to optimize via NTCP/TCP modeling Raystation via built in radiobiological optimizer.