COMMENTARY

Muscle Power to Cancer Patients

David J. Kerr, CBE, MD, DSc, FRCP, FMedSci

Disclosures

June 03, 2014

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Hello. I am David Kerr, Professor of Cancer Medicine at the University of Oxford. In clinic on Friday, I saw a young patient who was receiving adjuvant chemotherapy after resection of a colon cancer. He was in his late 30s and he had his family with him. I noticed that when he stooped to pick up his 3-year-old daughter before coming into my office, he had real difficulties in doing so. It made me think about the very interesting link between muscle function and muscle mass.

Skeletal muscle is the largest organ in the body and in lean individuals; it accounts for 40%-50% of body mass. It's an important organ, highly glycolytic, and is known to play an important prognostic role in all-cause mortality, cancer, and cardiovascular disease. Typically, I only consider muscle function when I think about cachexia -- the patients who suffer extreme muscle wasting. Patients with advanced pancreatic cancer have a huge reduction in muscle mass. It's a much more pervasive phenomenon than I had considered. A lot of work across most tumor types[1] suggests that many of our patients (compared with age, sex, and body weight-matched control subjects) have perhaps as much as 1-2 kg less muscle mass. At a time when we are paying more attention to the physical activity of our patients, it's worthwhile thinking about this.

What could cause the level of muscle dysfunction in the young patient that I saw in the clinic? Most of our patients are elderly, and the elderly lose muscle mass with advancing age. Malnutrition is another factor. The patients who we see in our gastroenterology practice are not sufficiently well nourished and can lose muscle mass as a result. The proinflammatory state induced by cancer results in high levels of tumor necrosis factor-alpha and interferon gamma, and through nuclear factor-kappa B, this causes cytolysis of skeletal muscle. Other lifestyle factors come into play, such as physical inactivity. Our patients who have impaired performance status tend not to exercise as much as when they are fully fit.

Treatment is another element that can impair muscle function. People have looked at the impact of treatment with conventional cytotoxic drugs on muscle mass. Bevacizumab, for example, has been associated across a course of treatment with the loss of 1-1.5 kg of muscle mass, as has androgen deprivation therapy in prostate cancer, 5-fluorouracil in the adjuvant setting in colon cancer, and doxorubicin in breast cancer. Look at some of the drugs that we use as supportive agents. For example, glucocorticoids used as mediators of antiemesis can cause muscle wasting.

Observational studies and some randomized trials are starting to suggest that patients who exercise more and gain more muscle mass have better outcomes.[1] I have been in the habit of saying to patients that if you feel tired, listen to your body. Your body is telling you something, so take a nap. It's not about giving in to the cancer but just listening to your body. I might start to reverse that rather blind advice and talk more seriously about exercise. Take the dog for a walk, making sure you that have 30 minutes of exercise every day. I might even consider rather more thoughtful exercise regimens, such as exercise programs that are tailored to the age category of patients that we are seeing. It's something to think about.

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