In their article in this issue, Drs. Jatoi and Loprinzi review much of the data on weight loss and anorexia in cancer patients from the standpoint of the impact of nutrition and various pharmacologic agents on management, and they make some sound recommendations for therapy. The benefit of nutritional interventions in this area are often overhwhelmed by the patient’s complex disease course and, therefore, are difficult to demonstrate.
It is now clear that malnutrition occurs for many different reasons, but that the metabolic abnormalities associated with cancer are largely due to the host’s response to the tumor. In a sense, these abnormalities are an unavoidable component of the immune response, but many patients with cancer lose weight at the same rate as other malnourished patients with chronic diseases.
Some cancer patients, especially breast and prostate cancer patients, are not malnourished but obese. Therefore, it may be helpful to classify the nutritional approach to cancer patients based on a more global understanding of the role of nutrition in cancer prevention and treatment rather than simply looking at weight loss therapy in isolation.
It has been estimated that in adults over age 50 years, one of two men and one of three women will be diagnosed with some form of cancer during their lifetime. Many of these people will be successfully treated cancer survivors who will be interested in preventing a recurrence of their disease. Weight loss in an obese cancer patient may be desirable. For example, a reduction in body fat can lead to a reduction in circulating estradiol(Drug information on estradiol) levels in postmenopausal breast cancer patients. Moreover, the institution of a healthy diet rich in fruits and vegetables may, in turn, lead to significant weight loss.
Normal Starvation vs Cachexia
In true cancer cachexia as opposed to normal starvation, weight is lost disproportionately from protein stores. Calorie restriction of normal volunteers leads to a 0.25-lb loss of lean mass per pound of weight lost. Disproportionately greater losses from muscle, due to the effects of cytokines in patients with an active cancer that interferes with normal adaptation to starvation, can lead to impaired immune function. However, in most studies the adaptive loss of muscle mass associated with simple starvation has not been adequately separated from the disproportionate and rapid loss of muscle mass that increases the risk of infection. In many malnourished cancer patients, there is no evidence of malnutrition beyond that which results from the adaptive response to reduced food intake, and rapidly progressive general weight loss is much less common than the disproportionate weight loss associated with cancer.
The End-Stage Patient
Twenty years ago, I routinely administered total parenteral nutrition to end-stage cancer patients. While this produced some salutary effects in selected patients, the risk-benefit considerations articulated in a number of reviews and meta-analyses have convincingly argued against routine use of total parenteral nutrition in end-stage patients.
The Weak Patient Undergoing Therapy
Anorexia and weakness routinely develop in many patients undergoing chemotherapy or radiation. Such patients should be encouraged to rest adequately and avoid skipping meals. Nutritional supplements in liquid form are particularly useful in this population.
As the result of depression, many cancer patients fail to eat at all and suffer undue amounts of fatigue. On the other hand, some patients equate weight loss with poor outcome and fight to gain weight during therapy to prove that they are prevailing over their cancer by eating high-fat desserts and red meats. Some patients even become obese in the process, and this should not be encouraged. The period of therapy is usually brief when viewed in the context of the patient’s overall life span, and if the likelihood of response is high, then nutrition during therapy should take a backseat to quality-of-life issues.
The Patient Who Wants Nutritional ‘Therapy’
Many cancer patients obtain information on nutrition from books, friends, health food stores, and the Internet. It is important to advise these patients that nutrition is not a therapy for cancer, but rather it is a body of information in the scientific literature that suggests that healthy nutrition including fruits, vegetables, cereals and grains, reduced dietary fat, and the achievement and maintenance of a healthy body weight may be beneficial in cancer prevention. Although the benefit of nutritional advice in reducing cancer recurrence is far from certain, it can reduce the risk of other chronic diseases. Some patients also enjoy an improvement in their quality of life from making nutritional and lifestyle changes.
As Drs. Jatoi and Loprinzi discuss, patients presenting with weight loss and anorexia should receive nutritional counseling and pharmacologic therapy as necessary. With increased attention to the nutrition of cancer patients at all stages of treatment, medical oncologists can provide benefits by (1) enhancing the physician-patient relationship, (2) obviating needless alternative therapies, (3) improving quality of life, and (4) preventing the development of malnutrition through early intervention. Future research on gene-nutrient interactions in cancer prevention and treatment will point the way to new approaches.