Systematic review of dose--volume correlates for structures related to late swallowing disturbances after radiotherapy for head and neck cancer.

BACKGROUND: We analyzed published dose-volume data of the structures related to late radiotherapy-induced swallowing disturbances in head-and-neck cancer to estimate their sensitivity, specificity, and predictive value and to propose minimal criteria for future studies.
METHODS: We performed a systematic literature search to identify dose-volume correlates with late swallowing disturbances. Study design, dose-volume data, toxicity evaluation, and statistical methods were considered in the analysis.
RESULTS: Seven studies were found, among which one prospective study reported exact dose-volume correlates for individual swallowing structures. Four studies identified dose-volume correlates without reporting exact numbers. One study did not find any correlate of dose-volume data of the swallowing structures with late swallowing disturbances. Variations in patient characteristics, study design, methodology, and statistics made any comparison difficult. However, mean dose to the pharyngeus constrictor muscles appeared to be the most demonstrative predictor of late swallowing disturbances, e.g., reducing the mean dose to the pharyngeal constrictor muscles from 61-64 to 52-55 Gy resulted in fewer swallowing disturbances. There were no available data to estimate sensitivity, specificity, or predictive value of the reported dose-volume correlates.
CONCLUSION: Mean dose to the pharyngeal constrictor muscles appeared to be the most important dosimetric predictor of late swallowing disturbances. Suggested dose-volume correlates require validation in prospective well-designed clinical trials, applying appropriate statistical methods that would account for possible interfering factors.