Exploring the nature and impact of taste dysfunction in people receiving chemotherapy

Abstract

Self-reported ‘taste’ problems are common in people receiving chemotherapy and have implications for nutritional and psychosocial domains. Taste refers to the perception derived when chemical molecules stimulate taste receptor fields in the oral cavity whereas flavour perception involves at least three independent sensory systems including taste, smell and texture. Conflation of the terms taste and flavour contributes to clinician confusion and reduces the opportunity to develop effective strategies to address taste problems in cancer patients.

The research reported in this thesis aimed to characterise the extent to which taste function and food hedonics contribute to the eating and drinking experience in people receiving chemotherapy and to investigate how this is managed in the clinical setting. There was a mixed methods approach to this program of research that was comprised of three separate studies, in two phases, designed to:

Phase 1, qualitative

1. Describe current practice surrounding taste function and food hedonics in the clinical oncology setting (Study 1);

2. Understand the experience and consequences of altered taste function and food hedonics for people receiving chemotherapy (Study 2); and

Phase 2, quantitative

3. Describe the patterns of altered taste function and food hedonics across the chemotherapy treatment trajectory (Study 3).

In the Phase 1 studies, patient and clinician interviews were used to explore a) clinician practice regarding the management of taste problems and b) patient and carer descriptions, experiences and consequences of taste changes. This qualitative phase informed the quantitative phase of the research: a longitudinal study of 52 women receiving chemotherapy for breast cancer that assessed taste function, appetite and food liking six times from before chemotherapy to 2 months after chemotherapy and investigated whether changes in these outcomes were associated with dietary intake, nutritional status or social dining activity.

Phase 1 findings demonstrated that ‘taste’ problems refer to a raft of issues related to the wider aspects of flavour including changes to the sense of smell or touch, or to problems with appetite or food liking. Clinicians have limited capacity to distinguish between these scenarios. These changes shaped what patients chose to eat, drink, cook and purchase, and influenced how they dined and how they felt. A need for new approaches to classifying and describing flavour problems was identified and a requirement for better quality information and evidence with which to guide patients was indicated.

In Phase 2, patterns of taste and hedonic changes were characterised in an unprecedented fashion across the treatment trajectory. Findings from Phase 2 analyses showed taste function and food hedonics were adversely influenced with greatest change closest to chemotherapy administration, followed by a gradual return to baseline measures. Problems resolved by 2 months after completion of chemotherapy. Change from baseline in ability to correctly identify all tastants was significant early in the third chemotherapy cycle (difference = 18.2%; 95% CI = 2.7, 32.9; p = 0.02) and final chemotherapy cycle (difference = 19.6%; 95% CI = 3.0, 35.1; p = 0.02). Decreased liking of sweet food (chocolate) was observed in the early (d = 0.77; p = 0.002) and middle stages of the third chemotherapy cycle (d = 0.70; p = 0.003) and early in the final chemotherapy cycle (d = 0.89; p = 0.001). Appetite was significantly decreased from baseline early in both the third and final chemotherapy cycles (d = 1.02; p < 0.001 respectively).

Associations were found between taste and hedonic changes and dietary intake, nutritional status and social dining. Change in ability to correctly identify tastants was associated with reduced energy intake (r = 0.32; p = 0.005) early in the third chemotherapy cycle. At this assessment point, decreased liking of a sweet food item was also associated with reduced energy intake (r = 0.35; p = 0.001). Appetite loss was associated with reduced energy (r = 0.35; p = 0.001) and protein intake (r = 0.36; p = 0.001) early in a chemotherapy cycle, decrease in BMI over the study period (r = 0.36; p = 0.001), and change in overall nutritional status as assessed by PG-SGA score (r = 0.18; p = 0.09). Early in the final chemotherapy cycle, small-sized but non-significant associations were seen between taste change and social dining episodes (r = 0.22, p = 0.09) and between appetite loss and social dining episodes (r = 0.18, p = 0.16).

Clinicians are ill equipped to support patients who report taste problems due to an absence of assessment tools or classification symptoms to identify problems described colloquially as ‘taste’. An emerging taxonomy of taste arising from this research goes some way to address the need for a classification system linking patient language to specific sensory or hedonic disturbances. Research findings will be used to guide the development of more specific pre-chemotherapy education material for patients.