ESTRO 2025 - Abstract Book

S974

Clinical – Head & neck

ESTRO 2025

1342

Mini-Oral Impact of radiation dose to the swallowing organs on death from aspiration pneumonia in oral cavity cancer Jhen-Bin Lin 1 , Jie Lee 2 , Yu-Jen Chen 2 1 Radiation Oncology, Changhua Christian Hospital, Changhua, Taiwan. 2 Radiation Oncology, MacKay Memorial Hospital, Taipei, Taiwan Purpose/Objective: Aspiration pneumonia is a major cause of non-cancer mortality following radiotherapy for head and neck cancer. The radiation dose delivered to the swallowing structures may be a target to lower the risk of death from aspiration pneumonia ( Figure 1 ). This study aims to investigate its incidence and risk factors in patients receiving adjuvant radiotherapy for oral cavity cancer (OCC). Figure 1 Representative axial dose distribution (54-60 Gy) of radiotherapy from upper to lower neck (A–C). The superior, middle, and inferior pharyngeal constrictor muscle (blue, green, and pink), supraglottic larynx (cyan), and glottic larynx (light green) were delineated.

Material/Methods: We enrolled 1043 patients with OCC who underwent surgery and adjuvant intensity-modulated radiotherapy between 2010 and 2020 at two tertiary centers. Mean radiation dose delivered to the superior, middle, and inferior pharyngeal constrictor muscles (sPCM, mPCM, and iPCM), cricopharyngeus muscle, and larynx were compared between patients who died from aspiration pneumonia and those who were alive or died from other causes. Results: The median age was 55 (IQR: 47–62) years, and 915 (87.7%) patients were male. Median follow-up was 5.4 (IQR: 2.9– 8.7) years. Among patients with non-cancer mortality ( n =90), aspiration pneumonia was the major cause of non cancer mortality in 56 (62.2%) patients. Patients who died of aspiration pneumonia were more likely to be smokers and have Eastern Cooperative Oncology Group (ECOG) 1, pT3–4, pN2–3, positive margin, and extranodal extension. The mean dose delivered to the swallowing structures was higher in patients who died of aspiration pneumonia (all p <0.05). In multivariable analysis adjusted for age, ECOG, smoking status, pathological tumor and nodal stage, margin status, and extranodal extension, a higher mean dose to the sPCM, mPCM, iPCM, cricopharyngeus muscle, and larynx was independently associated with an increased risk of death from aspiration pneumonia (all p <0.05). The threshold mean dose (structures) for lowering the risk of death from aspiration pneumonia was 52.7 Gy (sPCM), 50.9 Gy (mPCM), 46.2 Gy (iPCM), 44.2 Gy (cricopharyngeus muscle), 47.1 Gy (supraglottic larynx), and 45.5 Gy (glottic larynx) (all p <0.05) ( Figure 2 ).