Gustatory function following radiotherapy to the head and neck

Abstract

An intact sense of taste provides pleasure, supports sustenance and alerts the body to potential toxins. Patients with head and neck (HNC) who undergo radiotherapy (RT) are at high risk of developing acute and late taste dysfunction leading to poor oral intake, reduced nutritional status and reduced quality of life (QoL). Technical advances in the delivery of RT and the introduction of intensity-modulated proton therapy (IMPT) offer the opportunity to develop taste preserving strategies by reducing the dose delivered to the gustatory organs-at risk (OAR). The aim of this thesis is to study the temporal loss and recovery of taste dysfunction following RT to the head and neck. Chapter 2 is a systematic review and prevalence meta-analysis of 31 studies reporting gustatory outcomes following RT to the head and neck. This chapter confirmed that acute taste dysfunction is common (seen in as many as 96% of patients) and important post RT but also highlights the paucity of high-quality research in this area. Chapter 3 compared patient reported outcomes (PROs) in bilateral versus unilateral RT to the head and neck and explored the relationship between patient reported and clinician reported measures of taste dysfunction, with the latter showing only a 37% sensitivity for the former. Chapter 4 analysed data from a large multi-centre longitudinal study with patient reported gustatory outcomes from over 5000 patients at baseline, 4 months (m) and 12m following diagnosis and treatment for HNC. In those treated with RT or chemo-RT , tumour site was strongly associated with 4m taste dysfunction (oropharynx vs others OR 3.15, 95% Cl from 2.53 to 3.91). These chapters on retrospectively analysed cohorts providing PROs were then supplemented with data collected in two novel studies at the Royal Marsden Hospital (RMH). Chapter 5 was a cross-sectional study of patients 12m following completion of radiation. Chapter 6 was a prospective study with outcomes collected at baseline, end of treatment, 2m, 6m and 12m. Both of these chapters showed that dose to the anterior two-thirds of the tongue was higher in those with taste dysfunction (mean 43.1 Gy vs 32.0 Gy, p=0.013) and that those receiving lower doses were much less likely to experience dysfunction (0-20 Gy 42.9% PRTD vs 20-30 Gy 77.8%).