Understanding Cachexia: Weight and Muscle Loss Associated with Cancer

Cachexia is a serious stage of malnutrition that occurs in severe illnesses like cancer and other long-term diseases where the body wastes away. It's different from just being hungry because it involves not only losing weight but also losing muscle and fat. This makes it hard for treatments to work and worsens the patient's prognosis and quality of life.

Doctors call the loss of muscle and fat in cachexia "sarcopenia" or "myopenia". Unlike when someone is just not eating enough, where they might lose fat but keep muscle, in cachexia, both muscle and fat are lost. Because cachexia is complicated and can change a lot depending on how a person is fed or treated with drugs, it's tricky to have one clear definition that everyone agrees on. Plus, understanding why it happens and finding good treatments for it is still a big challenge for doctors and researchers.

In 2017, the European Society for Clinical Nutrition and Metabolism (ESPEN) classified cachexia as a type of malnutrition linked with chronic diseases and inflammation.

Understanding Cancer-Related Cachexia

Cancer-related cachexia is different from both starvation (not eating enough without a disease) and malabsorption (not absorbing nutrients due to a disease but without inflammation). When cachexia starts but symptoms aren't severe yet, it's called "pre-cachexia". A group called the cachexia special interest group (SIG) has defined this and says it's important to deal with it early.

Sometimes, cachexia gets very serious, called "late cachexia" or "severe cachexia", where improving nutrition isn't possible anymore. In the EPCRC guidelines, this is called "refractory cachexia" and means the condition is very hard to treat because of resistant cancer or it's getting worse very quickly.

As cancer progresses, cachexia often sets in, leading to irreversible malnutrition and eventual death. However, some types of cancer are less likely to cause cachexia, and how fast it progresses can vary from person to person. Cachexia disrupts the body's metabolism due to widespread inflammation and increased breakdown of muscle and fat. This shows up as symptoms like muscle loss, insulin resistance, and fat breakdown. When this metabolic problem becomes severe, the body can't use food properly, and malnutrition becomes permanent. Therefore, it's crucial to start providing extra nutrition early on, before cachexia becomes too severe and the body can't recover.

Causes and Effects of Cachexia

Loss of Appetite

Loss of appetite is observed in approximately 40% of cancer patients and has a prevalence of 80% in patients with advanced-stage cancer. Some causes of loss of appetite in cancer patients are nausea, the cancer itself, pain, anxiety, and depression. Recently, it has been suggested that anorexia is caused by an increased inflammatory response.

Abnormal Energy Metabolism

Cancer cells consume more glucose than normal for survival, leading to unbalanced energy production. This mechanism significantly contributes to the increased energy expenditure observed in cancer patients.

Increased Insulin Resistance and Abnormal Metabolism

In cancer patients, the way their bodies handle sugar, fat, and protein becomes disrupted. Their liver starts making more sugar, while their muscles become less sensitive to insulin, the hormone that helps control blood sugar. This means they have trouble using sugar properly, even before they start losing muscle mass.

Changes in Neuroendocrine System

In cancer cachexia, hormones that help build muscles and regulate hunger change. A hormone called insulin-like growth factor-1 (IGF-1), which helps muscles grow, decreases, leading to muscle loss. Another hormone called leptin, which controls appetite, decreases too, while a hormone called ghrelin, which makes you feel hungry, increases.

Current Medical Guidelines

Current medical guidelines recommend monitoring and performing preventive nutritional interventions in the case of pre-cachexia, in which weight loss is significant due to loss of appetite.

Nourishment Route

For cancer patients, it's best to try eating by mouth or using a feeding tube if they can. Feeding through a tube is seen as an extra way to help with treatment. According to ESPEN guidelines, eating by mouth or using a tube is the first choice for nutrition in cancer treatment. If eating by mouth is hard, like with head and neck or esophageal cancer, doctors might suggest using a feeding tube that goes into the stomach through the nose or a small hole in the stomach called a gastrostomy. Feeding through a tube is only recommended when eating by mouth or taking supplements isn't possible.

Energy Dosing

For cancer patients, the amount of energy they need to eat is adjusted based on how bad their metabolic problem is. The energy needs vary depending on the type of cancer and how advanced it is. When inflammation is high, their energy needs go up. Usually, cancer patients are less active, so they need less energy. When cancer gets really bad and doesn't respond to nutrition, the amount of food given is reduced towards the end. At the very end of life, even if given food, the body might not use it properly and it can even cause harm.

Infusion Management for Late Stage

In Japan, when cancer patients can't eat enough, they often get fluids through a tube. But sometimes, giving fluids can make things like swelling, fluid in the chest or belly, and more mucus in the airways worse. When deciding whether to give fluids, doctors listen to the patient and family and weigh the benefits against the risks.

Nutrition Therapy

Giving advice, counseling, and education about nutrition to cancer patients can help them eat better and feel better. Sometimes, patients and families don't know how important eating well is, so guidance from a doctor or dietitian is important.

Exercise Therapy

Cancer patients often aren't as active, which can lead to muscle loss and tiredness. Light exercises like walking can help keep muscles strong. But at the very advanced stage of cachexia, too much exercise can make things worse if they can't eat enough or their metabolism is really messed up. Some patients who stick to an exercise plan can feel a lot better, but many find it hard to keep up with. Doing group exercises or intense workouts might mean more trips to the hospital, which can be tough on patients.

Other Treatment Modes

Other treatment modes are medicines like NSAIDs, corticosteroids, and oral supplements under the physician’s supervision. Even though many people with advanced cancer suffer from cancer cachexia, many don't get diagnosed officially. It's crucial to spread the word about cancer cachexia and find new treatments that not only help with the symptoms but also make life better for those dealing with it.