Anatomical changes in the pharyngeal constrictors after chemo-irradiation of head and neck cancer and their dose–effect relationships: MRI-based study

Abstract

Purpose-Dysfunction of pharyngeal constrictors (PCs) after chemo-irradiation of head and neck (HN) cancer has been proposed as major cause of dysphagia. We conducted prospective MRI study to evaluate anatomical changes in the PCs after chemoirradiation, to gain insight of the mechanism of their dysfunction and their dose-effect relationships. The PCs were compared to the sternocleidomastoid muscles (SCMs), which receive high doses but do not relate to swallowing.Patients and Methods-Twelve patients with stage III-IV HN cancer underwent MRI before and 3 months after the completing chemo-irradiation. T1-and T2-weighted signals and muscle thickness were evaluated for PCs (superior, middle, and inferior), and SCMs. Mean muscle doses were determined after registration with the planning CT.Results-T1-weighted signals decreased in both PCs and SCMs receiving >50 Gy (p<0.03), but not in muscles receiving lower doses. T2-weighted signals in the PCs increased significantly as the dose increased (R 2 =0.34, p=0.01). The T2 signal changes in the PCs were significantly higher than the T2 changes in the SCMs (p<0.001). Increased thickness was noted in all PCs, with muscles receiving >50 Gy gaining significantly more thickness than PCs receiving lesser doses (p=0.02). In contrast, the SCM thickness decreased post-therapy (p=0.002).Conclusions-These MRI-based findings, notably the differences between PCs and SCMs, suggest that underlying causes of PC dysfunction are inflammation and edema, likely consequential to acute mucositis affecting the submucosa -lying PCs. These results support reducing mean PC doses to ≤50 Gy, as well as reducing acute mucositis, to improve long-term dysphagia.

Physiological Changes to the Swallowing Mechanism Following (Chemo)radiotherapy for Head and Neck Cancer: A Systematic Review

“…Whilst the notion of the general resistance of skeletal muscle to RT is well-accepted [55], it has been postulated that the PHYSIOLOGICAL SWALLOWING DEFICITS FOLLOWING (C)RT FOR HNC 13 pharyngeal constrictor and laryngeal adductor muscles and epiglottic walls, which are situated in close proximity to the submucosa, may be secondarily affected by the acute radiation-induced inflammatory response of these mucosal layers, culminating in the loss of elasticity and therefore dysfunction of the laryngeal and oropharyngeal musculature [32,56].…”

Volumetric Change of Selected Organs at Risk During IMRT for Oropharyngeal Cancer

“…Besides adaptive implications, the present data provide insights on the pathophysiology of the damage induced by RT. The swelling of both the CM and the L a few months after the end of RT has been documented (18)(19)(20). Investigators at the University of Michigan showed an increase in thickness of the retropharyngeal space by CT 3 months after chemoradiotherapy (18).…”

Dysphagia in head and neck cancer patients treated with radiotherapy and systemic therapies: Literature review and consensus

“…All these abnormalities can be responsible for an altered swallowing process and for a post-swallowing residue in the oropharynx, valleculae and hypo-pharynx, which may subsequently be aspirated. Radio-induced dysphagia can often be associated to altered sensitivity, which may cause a silent aspiration and deficient cough reflex [15,[70][71][72][73][74].…”