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| Prevention of Radiation-Induced Dysphagia (pp. 27-48) |
$100.00 |
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Authors: (Piet Dirix, Sandra Nuyts, Department of Radiation Oncology, Leuvens Kankerinstituut (LKI), University Hospitals Leuven, Leuven, Belgium)
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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
priority. |
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