The Impact of Cancer on Nutrition
Cancer impacts nutrition through local effects caused by the tumor and by altering metabolism. It has been shown that at the time of diagnosis, 80% of patients with upper GI cancer and 60% of patients with lung cancer have already experienced significant weight loss, defined as a loss of at least 10% of body weight in 6 months (National Cancer Institute [NCI], 2011). Weight loss is an indicator of poor prognosis in people with cancer.
Local Tumor Effects
Local tumor effects occur when the tumor impinges on surrounding tissue, impairing its ability to function. The effects vary with the site and size of the tumor and are most likely to impact nutrition when the GI tract is involved (Table 22.2). GI obstruction can cause anorexia, dyspha- gia, early satiety, nausea, vomiting, pain, or diarrhea, leading to weight loss and malnutrition.