Cancers of the upper aerodigestive tract account for around 4% of all malignant tumours worldwide. Colon and liver cancer are the most common digestive cancers. The epidemiology of liver cancer is changing, and the number of deaths from liver cancer has increased by 25% worldwide. In France, around 19,000 cancers of the upper aerodigestive tract and 88,000 new cases of digestive cancer are diagnosed each year (colon cancer remains the most common). Patients with these two types of cancer are at particularly high risk of undernutrition.
In cancer patients, changes in diet may result from constraints linked to the cancer or possible after-effects, but also from personal choices (for example, adopting a healthier diet). Cancer and its treatment lead to changes such as increased nutritional requirements and hypercatabolism, or sensory changes (taste and smell), reducing pleasure and food intake. These problems will impair quality of life and intensify undernutrition, a major problem in the management of the disease since it increases the risk of complications, therapeutic failure and mortality. It is estimated that 10-20% of deaths in cancer patients are attributable to the consequences of undernutrition rather than to the disease itself. In the VICAN study, 41% of patients changed their diet after diagnosis: 29% because of changes in taste and 82% to have a healthier diet. These changes were associated with the treatment received, the presence of sequelae and anxiety.
Taste and smell disorders are common in different types of cancer (any solid or haematological type) and treatments (chemotherapy, radiotherapy and surgery. The mechanisms involved in sensory changes are not fully understood, especially in cancer, and with different types and treatments. Several hypotheses have been proposed: altered expression of enzymes of the oral sphere, altered expression of sensory receptors, saliva composition and function, and impact of the oral microbiota.
The early identification of undesirable effects linked to nutrition, and the early or anticipated diagnosis of undernutrition are important issues in the management of cancer patients. The pleasure (or displeasure) produced by food guides desire and eating behaviour. The mechanisms involved are linked to hedonic sensations: conditioned satiety, specific sensory satiety, negative alliesthesia and the reward system (hedonic system). The latter is influenced by the environment and can be consciously controlled, with several dimensions: liking (the patient likes or dislikes a given food) and wanting (evaluates the desire to consume a given food at a given moment). All these parameters, together with sensory and dietary learning throughout life (habits, beliefs and constraints), influence food preferences and therefore eating behaviour. Individual sensitivities and the personal history of the disease (treatment and care pathway, sequelae, presence of co-morbidities, etc.) must therefore be taken into account when setting up preventive actions for cancer patients. It seems important to explore these factors, the experience of patients and the consequences for eating behaviour in daily life, in order to improve support and communication with healthcare professionals, as well as prevention and early detection of undernutrition. It would be interesting to conduct more in-depth studies on nutritional status, quality of life and changes in taste and smell, which in most studies have been considered separately.