Cancer Cachexia Syndrome

3. Cancer Cachexia Syndrome

Distinction Between Weight Loss Due to Starvation and Cachexia

It is well recognized that weight loss is a common finding in human cancer patients and one which has been shown to have associations with clinical outcome (Tisdale, 1997). As already stated, weight loss in association with neoplasia can occur for a number of reasons including the effects of the tumor and the cancer therapy. However, the weight loss seen in many human cancer patients does not appear to be attributable to decreased food intake alone. In simple starvation, individuals lose principally adipose tissue, whereas patients with neoplasia can experience loss of both lean and adipose tissues (Moley et al., 1987). Furthermore, the magnitude of the weight lost often does not correspond to the amount of food consumed, and this weight loss cannot be reversed by a concomitant increase in caloric intake (Costa et al., 1980).

This paraneoplastic syndrome of cancer cachexia is hypothesized to result from metabolic alterations that exist as a consequence of the underlying tumor. Derangements in carbohydrate, lipid, and protein metabolism have been found in both human and canine cancer patients that may contribute to weight loss (Shapot & Blinov, 1974; Nixon et al., 1980; Nolop et al., 1987; Shaw & Wolfe, 1987; Vail et al., 1990; Tayek, 1992; McMillan et al., 1994; Ogilvie et al., 1994;1997; Vail et al., 1994; Dworzak et al 1998). There is also evidence that cytokines, including TNFα, IL-1, and IL-6, could play a role in these metabolic alterations (Gelin et al., 1991; Moldawer and Copeland, 1997).

What remains unknown is to what extent the weight loss seen in feline cancer patients is attributable to decreased appetite or the direct effects of the tumor or therapy on nutrient assimilation or metabolism and to what extent cancer cachexia syndrome (Figure 4) may be responsible. This is important because in the former situation careful attention to feeding management should be able to avert or ameliorate loss of weight and body condition, whereas in the latter situation, effective means of counteracting the progression of cachexia remain elusive.

Figure 4. Assessment of weight loss. Many feline cancer patients have already experienced weight loss at the time of diagnosis and are at risk of further deterioration in body condition during the induction phase of chemotherapy. (© K. Michel & K. Sorenmo).

Body Condition as a Prognostic Factor

Cancer cachexia syndrome has been implicated as a negative prognostic factor for survival, surgical risk, response to chemotherapy, and tolerance of treatment in human cancer medicine (Daly et al., 1979; DeWys et al., 1980; McCaw, 1989). There have been some preliminary studies in companion animal cancer patients looking at body condition and weight loss. When body condition was evaluated in dogs seen at the oncology service at the University of Pennsylvania only 5% of the dogs were considered significantly underweight with a BCS <2.5/5 (1= cachectic, 3= optimal; 5= obese) while 29% were classified as significantly overweight (>4/5) (Michel et al., 2004).

Conversely, an investigation of feline cancer patients at the same institution documented that up to 44% of cats with cancer treated through the oncology service had a BCS <3/5 (Baez et al., 2007).

Cats in remission are more likely to weigh more and have a higher body condition score.

This study also found that both a low BCS as well as a low body weight had a negative impact on prognosis. Both cats with solid tumors and cats with lymphoma have significantly shorter survival times if their BCS or their body weight were low. Furthermore, a positive correlation between remission status and BCS was found.

The presence of weight loss or cachexia was not found to be an independent negative prognostic indicator as it has been in similar studies in human oncology (Vigano et al., 2000). Nevertheless, the results suggest that weight loss and deterioration of body condition are significant problems in feline cancer medicine and may have consequences for response to treatment, remission duration and quality of life.