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Taste and smell
Dr. Paolo Bossi
Summary of the presentation given at the TAO Congress on 8/9 December 2016
Taste and smell alterations are so-called orphan symptoms, which Dr. Bossi defines as rare and neglected symptoms which are not assessed in classification systems and for which no effective treatment is available. At the TAO Congress 2016, themed “Tolerability of Immunotherapies”, Dr. Bossi spoke about the burden that taste and smell alterations present for patients as well as the causes of and possible treatments for these symptoms.
Studies with regard to patients’ perception of toxicities in cancer treatment have found that physicians frequently underrate the importance that dysgeusia, the distortion of the sense of taste, has for the patients. However, taste- and odour-related abnormalities in cancer therapy have a major impact as they can cause food aversion and malnutrition and thus lead to a low performance status which may make dose reductions necessary. As radiation- and chemotherapy-induced taste and smell symptoms can persist for up to 12 months after the end of the treatment, impairment of quality of life is frequently a long-term problem.
It is important to detect taste and smell disorders as soon as possible, but assessing their causes can be very difficult. These symptoms are not only influenced by the various cancer treatments (surgery, radiation, chemotherapy, targeted therapies and, possibly, immunotherapy), but also by other factors such as drugs, metabolic problems, smoking, ageing, infections, zinc deficiency, hepatic and renal diseases as well as neural injuries.
In his presentation, Dr. Bossi reviewed the available options for treating taste and smell alterations:
- Practical suggestions include avoiding the use of metallic silverware and food that taste metallic or bitter (such as red meat, coffee, tea), eating more high-protein, mildly flavoured food (such as chicken, fish, dairy products, eggs), adding seasonings and spices in order to enhance flavour, eating cold food, using agents that stimulate salivary secretion and practicing good oral hygiene.
- The use of intensity-modulated radiation therapy (IMRT) can reduce dryness in the mouth (xerostomia).
- Nutritional support, e.g. dietary counselling and supplements, may be useful when the risk of malnutrition is high and has been shown to have a favourable impact both on nutrition and dysgeusia.
- Zinc is a cofactor of alkaline phosphatase, the most abundant enzyme within the taste bud membrane. It may also play a role in the conformation of proteins involved in the regulation of the pores of taste bud microvilli. However, the outcomes of trials with regard to zinc vary considerably.
- New options that are still under investigation include the miracle fruit synsepalum dulcificum, which binds to taste receptors and generates a sweet sensation, thus masking unpleasant taste for a short time, as well as the TH cannabinoid marinol, which stimulates the orosensory reward pathway via endocannabinoid receptors, thus enhancing the enjoyment of food.
Dr. Paolo Bossi, Istituto dei Tumori, Milan, Italy