Cancer Fatigue and Loss of Energy During Cancer Treatment

Cancer fatigue isn't caused by one single thing. Many overlapping factors are often responsible, including: (5)

• The cancer itself: cancer puts a lot of strain on your body. Cancer can trigger inflammation and metabolic changes in the body, which may contribute to fatigue, reduced appetite, and loss of muscle mass. 
• Cancer treatment: Chemotherapy, radiotherapy, and other cancer treatments can disrupt your body's normal function and cause fatigue.
• Lifestyle changes: Extended periods of bed rest, not moving around much during cancer treatment, struggling to sleep, and eating less can make you feel fatigued. 
• Emotional stress: Worry, anxiety, or sadness associated with cancer can weigh you down.

What Cancers and Stages Cause Fatigue

The extent of cancer fatigue often depends on the kind of cancer and its stage. Some cancers cause more fatigue than others. Late-stage cancers are notorious for making you feel worn out and tired because of the large number of cancerous cells and more aggressive treatments. (6)

But no one rule fits all. Someone with a small cancer or lower cancer stage or a different type of cancer may experience fatigue as much as someone with a large tumour or later stage.

Cancers more likely to cause fatigue include:

• Breast cancer 
• Blood cancers
• Prostate cancer 
• Lung cancer 
• Ovarian cancer 
• Bowel/colorectal cancer 
• Bladder cancer 
• Brain cancer 

How Different Cancer Treatments Contribute to Fatigue 

Cancer treatments can also contribute to cancer fatigue. 

• Chemotherapy: There are many different chemotherapy regimens; fatigue can occur at any time of the cycles or between cycles. Your response to chemotherapy is likely to be individualized. Over time, these drugs can also cause anemia, which can in turn cause dizziness. They also cause nausea and loss of appetite, which affects nutrition and reduces energy. Chemotherapy can also cause muscle weakness and low energy. (7)
• Radiotherapy: Radiotherapy may cause fatigue because it destroys some healthy cells, and your body has to divert a lot of energy into repairing damaged tissues. The fatigue associated with radiotherapy may peak around one to two weeks after exposure or worsen halfway through depending on the regimen. (8)
• Hormone therapy: Hormone therapy can disrupt your metabolism, making you feel fatigued and tired. (9)
• Immunotherapy: Fatigue is a common side effect of immunotherapy, although the exact causes are not fully understood. Inflammation, immune activation, and treatment-related side effects may all contribute. (10)
• Surgery: Recovering from surgery puts demand on your body and can make you feel worn out. Pain can worsen this feeling. (11)
• Other medications: Drugs for supportive cancer care can contribute to weakness. These include steroids like dexamethasone, antibiotics and drugs like tamoxifen. (12)

If your treatments involve a combination of these, for instance chemotherapy and surgery, that can increase the fatigue you feel.

Other Contributors to Fatigue

Cancer fatigue may also be linked to: (13)

• Nutrition issues: Loss of appetite, feeling full too early, pain or difficulty in swallowing, or inability to digest food may prevent you from eating enough, so that you feel weak and tired. 
• Sleep disturbances: If you are not getting enough rest as a result of pain, insomnia, restlessness, or emotional stress, that can lead to fatigue. 
• Reduced physical activity: Less exercise can make you lose muscle, reduce your endurance levels, and make you feel weak. 
• Emotional and psychological stress: Anxiety, worry, and depression can wear you down and make you feel exhausted. 

Managing your cancer fatigue can help your strength return. This will involve managing your daily energy, performing safe and necessary exercise, getting adequate nutrition and hydration, receiving mental health support, among others. 

Safe Exercise and Physical Activity

You don't have to push your body to its limits. Gentle aerobic exercise like strength training, walking and guided physiotherapy can help you build lost muscle mass and increase energy. It helps to listen to your body. Pause when it says pause and keep going when you can. (16)

Nutritional Support

Balanced meals go a long way to manage cancer fatigue. (17) The right amount of energy, protein and healthy fats are essential. In times when your appetite is low, such as during or after treatment, small, regular snacks or nutrient-dense meals can help. If fatigue is accompanied by weight loss, reduced appetite, or difficulty eating, ask your healthcare team about referral to an oncology dietitian. They can help assess your nutritional needs, recommend strategies to increase calorie and protein intake, and determine if medical nutrition may be needed to help you reach your nutritional goals/meet your dietary needs. Medical nutrition like oral nutritional supplements are food for special medical purposes and must be used under medical supervision.

Sleep and Stress Management

Getting adequate rest and reducing stress can help you feel less fatigued. Poor sleep and increased stress can trigger the release of your stress hormone – cortisol – which can make exhaustion worse. Practice mindfulness, stretching and relaxation, and good sleep hygiene. (18)