Improved NTCP model for late radiation-induced aspiration based on dose delivered to specific aspiration-related OARs

Radiation-induced aspiration is a serious complication following (chemo)radiation for head and neck cancer. The standard set of swallowing organs at risk (SWOARs) does not include all aspiration-related organs (OARs). An alternative proposed in earlier work includes a definition and delineation atlas for additional OARs, called Functional Swallowing Units (FSU). The purpose of this study was to compare two NTCP models for late aspiration, based on either SWOARs only or the FSU concept.

Data from 189 patients were analysed. Aspiration at baseline (Asp_T0) and 6 months after treatment (Asp_T6) were scored according to Penetration Aspiration Scale (PAS). All SWOARs and FSUs were delineated and the DVH was recorded. Clinical factors and average dose (Dmean) to all aspiration-related OARs were included in multivariable analysis. Two models were built, model 1: including clinical factors and SWOARs only and model 2: including clinical factors, SWOARs and FSUs.

Both final models included Asp_T0 and Dmean to the supraglottic larynx as predictors. Model 2 included the dose to three additional OARs as a predictor: 1) Anterior Segment (floor of mouth/ thyrohyoid muscles) 2) hyoglossus/styloglossus muscles complex (HSG) 3) upper oesophageal sphincter (UES). Adding FSUs to model 1 resulted in significant model updates and model 2 performed better than model 1 (AUC 0.79 vs. 0.75).

NTCP models for late aspiration may be improved by including the dose to aspiration-related OARs, defined by the FSU concept. In addition to the supraglottic larynx, sparing of the Anterior Segment, HSG and UES could further decrease the risk of radiation-induced aspiration, but this remains to be confirmed in clinical studies.