Taste and smell are essential senses that work together, allowing us to perceive flavour.1 The sense of taste helps to regulate food intake by allowing us to decide quickly whether to accept or reject a food.2 Taste perception activates neuronal pathways, aiding the digestion, absorption and storage of nutrients.2 Taste also provides hedonic pleasure from eating.2
Disturbances in taste perception, known as dysgeusia, can occur for many different reasons, including disease and medication.1 Altered taste perception is especially important in cancer as it can lead to reduced food intake, weight loss, and malnutrition – all of which are linked to poor disease outcomes and lower quality of life.3
How common are sensory changes in cancer?
Taste changes affect up to 70% of patients with cancer.1 This compares with a reported prevalence of 20% in the general population.4 Taste changes have been reported before, during, and after treatment for cancer; in many different tumour types; and in patients receiving either chemotherapy or radiotherapy.1
Despite their near-ubiquity, taste changes in cancer patients are not always recognised by clinicians and researchers, leaving important questions unanswered.2 For instance, the physiological mechanisms underlying taste alterations have not been fully elucidated and there is no “gold standard” assessment tool.1
What type of sensory changes occur in cancer?
Sensory changes in patients with cancer occur as a consequence of the disease or its treatment . They manifest in various ways:5
- Taste aversion to some flavours
- Changes in mouth feeling
- Changes in flavour thresholds
- Changes in flavour preference
- Bad tastes in the mouth
- Variation in smell
Disturbances of all taste modalities have been reported in cancer patients. Hyper- and hypogeusia for salt and sweet tastes are widespread, while changes to bitter and sour have been reported.1
Metallic taste is also common; in a recent study, 16% of cancer patients receiving chemotherapy, radiotherapy, or targeted therapy reported a metallic taste. These individuals also tended to experience hypergeusia for sour and bitter tastes.6 In another study, breast cancer patients undergoing chemotherapy showed an altered preference for certain macronutrients rather than specific tastes.7
Taste and smell alterations are typically noticed by patients shortly after treatment begins and may persist for 6–12 months after treatment ends.1 Occasionally, cancer-associated dysgeusia is permanent.8