3572 - Association Between Radiotherapy Dose to Contralateral Substructures and Post-Treatment Dysphagia in Oropharyngeal Cancer
Presenter(s)
M. Naqvi1, F. Kaval2, K. Danielson3, J. Zhu4, and V. Takiar5; 1University of Cincinnati College of Medicine, Cincinnati, OH, 2UC Health, Cincinnati, OH, 3UC health, Cincinnati, OH, 4penn state health, University Park, PA, 5Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH
Purpose/Objective(s):
Although radiotherapy improves locoregional control and survival in head and neck cancer, treatment-related dysphagia remains a common toxicity. Current dose constraints focus primarily on the pharyngeal constrictors, despite the contribution of multiple additional structures to the complex process of swallowing. The dose–response relationship for many of these structures remains poorly defined. Using standardized outcome measures including the International Dysphagia Diet Standardization Initiative (IDDSI) and the Functional Oral Intake Scale (FOIS), we hypothesized that higher radiation dose to additional head and neck substructures could also be associated with worse swallowing.
Materials/Methods:
We conducted a retrospective single-institutional study of 78 patients treated with definitive or adjuvant radiotherapy for locally advanced oropharyngeal cancer between 2023 and 2024 for whom longitudinal swallowing data were available. Archived radiotherapy plans were reviewed, and swallowing-related structures including the genioglossus, mylohyoid temporalis, medial and lateral pterygoid, anterior and posterior digastric, masseter, and sternocleidomastoid were contoured using consensus organ-at-risk guidelines and confirmed by a diagnostic radiologist. Dosimetric parameters including mean dose, maximum dose, and volumetric metrics (V40%, V50%, V60%) were extracted. IDDSI and FOIS scores were obtained from routine speech-language pathology follow-ups. Bivariate correlation matrix and Spearman correlation were used to evaluate associations between radiation dose and swallowing outcomes.
Results:
Thirty-five patients met inclusion criteria. While high ipsilateral doses to normal structures are often unavoidable, we observed that higher radiation doses to contralateral masticatory muscles (including the contralateral masseter and medial and lateral pterygoid muscles) were negatively correlated with swallowing function at 3–6 months post-treatment (p<0.05). Persistent, statistically significantly negative correlations were observed for contralateral pterygoid V30 at 3–6 and 6–12 months following treatment and for contralateral medial pterygoid V30 and V40 and contralateral masseter mean dose and V30. (p<0.05 for all listed.) Additional significant dose–function relationships were identified across other swallowing-related structures.Conclusion:
These results suggest that radiation dose to contralateral masticatory muscles may also contribute to subacute and chronic swallowing dysfunction and long-term functional recovery in patients with locally advanced oropharyngeal cancer. Additional studies are warranted to further examine the role of prioritizing contralateral structures during treatment planning of oropharyngeal cancer patients receiving bilateral radiation therapy.