Previous papers in this symposium have been concerned largely with nutrition as a factor in the aetiology of cancer. It is right that we should be concerned with these aspects of the problem for a large proportion of oncological disease is environmentally induced and therefore at least potentially preventable. This is the more urgent for our attention because the results of treatment are far from good, at least for the more common kinds. Treatment of breast cancer, for instance, is scarcely more successful now in terms of five year, and certainly in terms of ten year, survival than it was forty years ago. It is equally urgent that we consider the nutrition of the patient with cancer, for the successful treatment of the disease is of little consequence if the patient dies of malnutrition in the process. Moreover, it may be that nutrition, and possibly individual nutrients, may be exploited to increase the effectiveness of treatment and that nutrition can therefore play an adjuvant role in the treatment of the disease.
Effects of cancer on nutritionMany patients with cancer show evidence of weight loss and reduction of body fat and muscle mass (Soukop & Calman, 1979). Many patients also have low concentrations of plasma albumin and biochemical indicators of vitamin status provide evidence of vitamin depletion. If this condition of malnutrition continues the syndrome known as 'cancer cachexia' develops. This condition is complex and is characterized by anorexia and early satiety, an increase in the basal metabolic rate (BMR) and energy expenditure, the development of anaemia, asthenia and changes in body composition. T h e increases in BMR, oxidative metabolism and plasma amino acid concentrations that occur in cachexia distinguish the condition from simple starvation and indicate that in cachexia there is a failure of adaptation to a reduced food intake. Cachexia is probably multifactorial in its aetiology and the biochemical changes leading to its development uncertain. There is evidence to suggest that tumours may produce peptides or other small molecules which when taken up by normal cells cause disturbances of the enzymes in those cells resulting in a condition of 'metabolic chaos', increase in energy expenditure and a release into the blood stream of amino acids and peptides which enter the metabolic pool and are taken up by the tumour for the growth of its own tissue (Theologides, Malnutrition in the cancer patient results from a poor food intake and this may be caused by a reduction in appetite, changes in taste perception, pain, mechanical obstruction and apathy and depression in the face of an uncertain or poor 1977).