Clinical Nutritional Assessment of Cancer Patients

2. Clinical Nutritional Assessment of Cancer Patients

The process of nutritional assessment involves evaluation of not only the patient’s nutritional status but also the diet it is receiving and how that diet is being fed. Furthermore, this process should not be an initial one time exercise but an on-going practice throughout the patient’s course of treatment so that adjustments can be made in diet and feeding recommendations based on the patient’s response to therapy. The actual task of nutritional assessment involves several steps (Figure 2). First determine the patient’s nutritional status which is a subjective evaluation based on the medical history and physical examination. Next the patient’s voluntary food intake should be assessed. Once the patient’s nutritional status and food intake have been evaluated, other aspects of the patient’s clinical presentation should be considered, including the specific type and stage of cancer, the intended course of therapy, and whether or not there are any pre-existing or concurrent medical conditions. Formulating a suitable nutritional plan for each patient needs to encompass all of this information.

Figure 2. A step-by-step approach for the nutritional assessment of feline cancer patients.

The nutritional assessment will help determine whether the patient is experiencing malnutrition or at risk of becoming malnourished, whether the diet and the intake of that diet are adequate to the patient’s nutritional needs, whether any specific dietary management, including assisted feeding, is indicated and, in the case of assisted feeding, which route of feeding will be the safest, most effective and best tolerated by the patient. The process of nutritional assessment can also identify potential problems that might arise as a consequence of the dietary management, and allow for planning to prevent them or anticipate them through appropriate monitoring.

Determining Nutritional Status

A technique referred to as subjective global assessment (SGA) was developed for the nutritional assessment of human patients approximately 20 years ago (Detskey et al., 1987). The technique was designed to utilize readily available historical and physical parameters in order to identify malnourished patients who are at increased risk for complications and who will presumably benefit from nutritional intervention. The assessment involves determining:
- Whether nutrient assimilation has been restricted because of decreased food intake, maldigestion or malabsorption;
- Whether any effects of malnutrition on organ function and body composition are evident;
- And whether the patient’s disease process influences its nutrient requirements

To adapt the SGA to cancer patients, the medical history should be assessed in five areas:
- Pre-existing or ongoing weight loss
- Extent of voluntary dietary intake
- The presence of persistent gastrointestinal signs either from the primary disease or treatment the patient is receiving
- The patient’s functional capacity (e.g., weakness, presence of exercise intolerance)
- And the impact of the patient’s underlying disease state.

When dealing with cancer patients one must consider the ways in which the tumor could directly or indirectly affect food intake, the impact that cancer therapy may have on food intake and metabolism, and the recognition that the tumor itself may exert effects on metabolism that negatively influence nutritional status.

It is often difficult to document a history of weight lost since most animals are only weighed when they come in to a veterinary clinic and not always then. It is critical that cats being treated for cancer are weighed consistently on the same scale and that the scale is sensitive and accurate for animals in the feline weight range. It is also important to know the time course over which the weight loss has occurred. Rapid weight loss is generally of greater concern because it is more likely to involve a greater percentage of lean tissue catabolism than a more gradual weight loss. Having said that, cancer cachexia syndrome, as documented in human cancer patients is characterized by loss of both lean body mass and adipose tissue and can take a chronic course.

Regardless of the reason a cat is presented at the clinic, the body weight must be recorded.

The physical examination focuses on changes in body composition, specifically wasting of fat stores and muscle mass, the presence of edema or ascites, the presence of mucosal or cutaneous lesions, and the appearance of the patient’s hair coat. Several excellent body condition scoring systems (BCS) have been developed for cats (Laflamme, 1997; German et al., 2006). However, these systems do not apply well to cats with cancer because they depict patients that deviate from optimal based on underor overconsumption of protein and calories. It has been reported in a study from the University of Pennsylvania that over 90% of cats diagnosed with cancer have evidence of muscle wasting even in cases where the patient had adequate or even excessive fat stores (Baez et al., 2007). Without careful examination, which involves palpation of skeletal muscle mass over bony prominences (such as the scapulae or vertebral column), some of these patients might be misclassified as overweight or even obese (Figure 3). Thus we recommend subjectively evaluating muscle mass (Table 1) in addition to using one of the standard body condition scoring systems available.

The findings of the historical and physical assessment are used to categorize the patient as:
A : well nourished
B : borderline or at risk of becoming malnourished
C : significantly malnourished.
Coupling this assessment with the patient’s cancer diagnosis, stage, treatment protocol, and prognosis will aid in making decisions about nutritional therapy.
Figure 3. Evaluation of the cat's body composition. (© K.Michel & K. Sorenmo).

Assessment of Voluntary Food Intake

In order to be able to assess whether that patient’s food intake is adequate, you must have a caloric goal, select an appropriate food, and formulate a feeding recommendation for the patient. By doing so, you will have an accurate account of how much food is offered to the patient, and will be able to evaluate the patient’s intake based on how much of the food is consumed.

Hospitalized Patients

For hospitalized patients, we recommend using an estimate of resting energy requirement (RER) as your initial caloric goal (Table 2) as most hospitalized patients are not expending much more energy than RER while they are caged. Under such conditions most patients eating at least RER will lose little if any weight. Clearly if a patient is willing to consume calories in excess of RER it should be permitted to do so. However, starting out with this amount of food will provide a goal to aim for with patients who have a decreased appetite. It is critical to monitor both the patient’s food intake and body weight to establish whether the patient is in energy balance or not and to permit timely adjustment of the dietary plan if the patient is not responding as anticipated (see Chapter 13)

Out-patients

The majority of cancer patients are treated as out-patients and therefore will require additional caloric intake to compensate for energy expended on voluntary physical activity. Under these circumstances, the daily maintenance energy requirement (MER) should be estimated (Table 3) and used to calculate the initial caloric goal.

This information should be converted into clear feeding directions for the cat’s caregiver using specific portions of whichever foods are being offered to the patient in a manner analogous to how a drug dosage would be calculated and prescribed. There should be a plan for reporting back to the clinician about daily food intake and for accurately monitoring body weight on a regular basis to assess the patient’s response and allow for modification of the feeding plan as appropriate.

Determining the Need for Assisted Feeding

Patients who are unable to eat or whose voluntary food intake is insufficient to maintain energy balance will require some form of intervention whether it is as simple as coax feeding or a more aggressive approach using some form of assisted feeding (see Chapter 13). Clearly the feeding management of those patients who are already significantly malnourished at the time of presentation should receive immediate attention.

It is often the case that reduced food intake as a consequence of cancer therapy can be anticipated. Therefore a plan should be in place for nutritional intervention should the need arise, particularly in the case of patients whose nutritional status is considered borderline at the commencement of therapy.