Radiation dose to dysphagia aspiration-related structures and its effect on swallowing: Comparison of three-dimensional conformal radiotherapy and intensity-modulated radiation therapy plans

Context: Radiotherapy techniques have improved over years but have also raised concerns over subsequent acute and late effects. One such complication, dysphagia, has led to much interest and optimization in treatment delivery. Aims: The aim of this study was to compare radiation dose to dysphagia aspiration related structures (DARS) in intensity modulated radiation therapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT), and assess its relation to post-treatment swallowing status, in patients of carcinoma of the anterior two thirds of tongue. Materials and Methods: Treatment plans of patients treated with IMRT and 3DCRT, from November 2011 to December 2012, were retrieved. Swallowing structures were contoured. Dose volume histograms were generated. Constraint doses were considered based on the statistical derivations. Swallowing status was evaluated based on University of Washington Head- and Neck-related Quality-of-Life questions addressing swallowing. Statistical Analysis Used: IBM SPSS Statistics 20 Windows (SPSS Inc., Chicago, IL, USA) was used. MannuWhitney U-test, Spearman's rho correlation coefficient, and receiver operating curves were used. Results: Definitive statistical and subjective correlations were found to exist between doses of swallowing structures, especially the constrictor muscles, the base of the tongue and larynx. Probable mean dose constraints derived statistically clinically corroborates with the swallowing status of patients. IMRT had statistically significant advantage over 3DCRT, in terms of V30 (P - 0.051), V50 (P - 0.002), V60 (P - 0.002), and D80 (P - 0.023) for swallowing structures taken together. Conclusion: Our study is probably one of the few studies predicting possible mean dose constraints for superior constrictor, the base of the tongue and larynx. Further prospective studies are required to confirm these and to improve the swallowing quality.