Effects of different radiation therapy techniques on swallowing function in individuals with nasopharyngeal cancer

Abstract

Nasopharyngeal cancer (NPC) is more common in the Southern China region than the rest of the world. Radiation therapy (RT) is the contemporary and standard treatment for nasopharyngeal cancer. Chronic complications arise from RT including hearing loss, xerostomia, trismus and dysphagia. Previous research has shown that dysphagia is prevalent in irradiated NPC patients. Radiation therapy techniques have improved in the last decade with the emergence of Intensity Modulated Radiation Therapy (IMRT), which allows more precise radiation beams directed at the tumor. In turn, it should also allow greater sparing of surrounding structures that are vital for preservation of swallowing function. This study was designed to investigate the difference in the degree of swallowing function preservation in two groups of irradiated NPC patients: the conventional RT and the IMRT group.

Thirty patients with NPC who received RT from 1998 to 2006 in Queen Mary Hospital, Hong Kong were randomly recruited during the period from January to December 2011. Participant’s swallowing competence and its effect on the quality of life was assessed by videofluoroscopic swallowing study (VFSS) and by the MD Anderson Dysphagia Inventory, respectively.

In comparison of swallowing performance with VFSS between the two groups, only one measure (Duration of Laryngeal Elevation) out of 13 showed significant difference on thin liquid and congee diet. Results from the MDADI did not show significant difference between the two groups.

From the results, it was concluded that IMRT only resulted in subtle improvement in preserving the swallowing function as compared to conventional RT. One possibility is the subject self-compensation of their swallowing impairments that led to functionally similar performance despite their differences in the anatomy and physiology. Swallowing is a highly complex body function and no single parameter can be used to accurately quantify and characterize one’s swallowing function. The interaction between the anatomical and physiological impairments resulted from radiation therapy and the compensatory mechanism could not be clearly explained with this study. Future research could adopt a longitudinal approach such that the changes in NPC patients who received radiation therapy can be better understood.