|Title: ||Prevention of radiation-induced dysphagia|
|Authors: ||Dirix, P|
|Issue Date: ||2012 |
|Publisher: ||Nova Science Publishers|
|Host Document: ||Dysphagia: risk factors, diagnosis and treatment pages:27-48|
|Article number: ||2|
|Abstract: ||Swallowing dysfunction after radiotherapy for head and neck cancer is correlated with compromised quality of life, anxiety and depression, and can lead to life-threatening complications such as aspiration pneumonia. Because the risk of radiation-induced dysphagia is associated with the use of concomitant chemotherapy and accelerated fractionation schedules, its incidence has considerably increased in recent years. More and more, dysphagia is recognized as the dose-limiting toxicity of head and neck radiotherapy. Highly conformal radiation techniques, such as intensity-modulated radiotherapy, have been successfully applied to spare salivary glands from high-dose radiation and prevent permanent xerostomia. It is to be expected that limiting the dose to the critical swallowing structures will similarly reduce the incidence of dysphagia.
However, several questions regarding which swallowing structures are essential, and what volume and dose constraints should be applied, remain to be answered.
Obviously, efficient swallowing is an extremely complex process, consisting of a series of coordinated events involving more than 30 pairs of muscles and 6 cranial nerves. Based on the physiology and anatomy of normal swallowing, a number of potential organs at risk for swallowing dysfunction have been identified. Correlating the dose to these structures with the presence of late dysphagia allows the definition of dose-response
curves. However, it is not clear how the endpoint of dysphagia should be best described. Objective assessment is possible through invasive techniques such as videofluoroscopy with modified barium swallow or fiberoptic endoscopic evaluation of swallowing. There are also several validated questionnaires for subjective evaluation, such as the EORTC QLQ-HandN35 swallowing subscale, consisting of 4 questions regarding swallowing of liquid, swallowing of pureed food, swallowing of solid food, and aspiration when swallowing. Experience in the evaluation of xerostomia has indicated that patient-reported endpoints are preferable.
Despite the use of different dysphagia endpoints, different sets of potential organs at risk and different patient populations, results of published studies determining the critical structures for the prevention of swallowing complications are remarkably consistent. Apparently, both
the mean dose to the pharyngeal constrictor muscles and the larynx, as well as the volume of those structures receiving 50 – 60 Gy, is significantly correlated with the occurrence of late dysphagia. These data imply that sparing these structures could prevent late dysphagia.
However, no clear dose or volume constraints can yet be proposed, and currently, the best approach consists of keeping the radiation dose to these structures as low as possible. On the other hand, avoiding underdosing to the targets in the vicinity should remain the highest
|Publication status: ||published|
|KU Leuven publication type: ||IHb|
|Appears in Collections:||Laboratory of Experimental Radiotherapy|