Risk reduction of radiation-induced aspiration by sparing specific aspiration-related-organs at risk; an in silico feasibility study.

Purpose: To assess the feasibility and benefit of NTCP optimized aspiration-prevention treatment planning by sparing specific aspiration related organs at risk, and to assess the impact of baseline complaints on the planning results.

Materials and methods: This in silico planning study included 30 HNC patients who were previously treated with definitive radiotherapy. New fully automated plans, allowing for sparing specific aspiration related organs at risk, were optimised directly on normal tissue complication probability (NTCP) models for common toxicities: xerostomia and dysphagia. Optimisation was performed with and without aspiration-prevention, i.e., with and without specific sparing of recently identified aspiration-related muscles, and with and without the assumption of existing baseline complaints.

Results: All plans complied with the pre-defined treatment planning quality criteria and were successful in limiting the risk of xerostomia and dysphagia. Aspiration-prevention VMAT, optimized using the additional NTCP model for aspiration, significantly reduced the estimated risk of late aspiration (p < 0.001) in all 30 patients when compared to plans without NTCP optimisation for late aspiration. The predicted risk of late aspiration was reduced even further when baseline aspiration was assumed present during optimisation, resulting in an average risk reduction of 13.3 % versus 8.3 % in plans assuming no aspiration at baseline. Aspiration-prevention did not reduce overall plan quality and maintained NTCP values obtained for various other toxicities.

Conclusion: Sparing specific aspiration-related organs at risk has the potential to significantly reduce the risk of late RT-induced aspiration, especially in patients who experience aspiration already at baseline.