Dose–response analysis of parotid gland function: What is the best measure of xerostomia?

Abstract

PurposeTo describe the dose–response relationships for the different measures of salivary gland recovery following radical radiotherapy for locally advanced head and neck squamous cell cancers (LA-HNSCC). Methods and materialsDosimetric analysis of data from the PARSPORT trial, a Phase III study of conventional RT (RT) and intensity modulated radiotherapy (IMRT) for LA-HNSCC was undertaken to determine the relationship between parotid gland mean dose and toxicity endpoints: high-grade subjective and objective xerostomia and xerostomia-related quality of life scores. LKB-NTCP parameters (TD50, m and n) were generated and tolerance doses (D50) reported using non-linear logistic regression analysis. ResultsData were available on 63 patients from the PARSPORT trial. Parotid saliva flow rate provided the strongest association between mean dose and recovery, D50=23.4Gy (20.6–26.2) and k=3.2 (1.9–4.5), R2=0.85. Corresponding LKB parameters were TD50=26.3Gy (95% CI: 24.0–30.1), m=0.25 (0.18–1.0 and n=1). LENTSOMA subjective xerostomia also demonstrated a strong association D50=33.3Gy (26.7–39.8), k=2.8 (91.4–4.4), R2=0.77). ConclusionWe recommend using the LENT SOMA subjective xerostomia score to predict recovery of salivation due to its strong association with dosimetry and ease of recording.