Cancer and your immune system
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IntroductionBack to top
The immune system is the body’s defence mechanism against illness and infection caused by bacteria, viruses, fungi (or yeasts), or parasites. These micro-organisms are sometimes collectively referred to as “germs”. Fighting infection or illness involves a large number of reactions and numerous cells and organ systems and is termed the “immune response”. 
There is a complex interaction between cancer and the immune system, mainly because:
- Cancer and its treatment(s) may weaken the immune system, whereas
- The immune system may help to fight cancer. 
The effects of cancer and its treatment on the immune systemBack to top
White blood cells are of paramount importance in the fight against infection and certain diseases. These cells are produced by the bone marrow. If cancer starts in, spreads to or invade the bone marrow, the body’s ability to produce white blood cells will be seriously reduced and thus the immune system will become weakened. Blood cancer (leukaemia) and cancer of the lymphatic system (lymphoma) are particularly known to compromise the bone marrow’s ability to produce white blood cells, but it can also happen with other cancers. 
Apart from cancer itself, certain cancer treatments may also temporarily affect immune system function by reducing white blood cell production in the bone marrow. Examples of such treatments are:
- Targeted cancer therapies
- Radiotherapy, and
- High doses of corticosteroids. 
Chemotherapeutic medicines target fast-growing cells – one characteristic that the vast majority of cancer cells have in common. Unfortunately, such medicines will also prove harmful to fast-growing healthy cells, such as those in the bone marrow and gut. By attacking fast-growing cells in the bone marrow, the body’s immune system becomes compromised as explained above. 
Targeted cancer therapies
Targeted cancer therapies, such as immunotherapy inclusive of cytokines and CAR T-cell therapy (see below), may in some instances damage healthy cells or damage or exhaust certain types of white blood cells, which will negatively impact the ability of the immune system to ward off infection. 
Radiotherapy is harmful to cancer cells through exposure to ionising waves of energy that either kill cancer cells or stunt their growth. Radio waves may also damage healthy cells and tissues, and thus weaken the body’s defences against infection and injury. 
Corticosteroids, which are also produced by the adrenal glands in the body in response to stressors, are often used as part of a cancer treatment regime because these medicines help to reduce inflammation produced by the tumour or its treatment. Steroids are also used to treat nausea and vomiting, stimulate a patient’s appetite and help reduce pain through their ability to reduce inflammation. While corticosteroids are sometimes utilised specifically to suppress the immune system after a stem cell transplant, this can also be a detrimental consequence of treatment. 
The immune system in the fight against cancerBack to top
Since cancer cells are different to normal cells, some cells of the immune system have the ability to recognise cancer cells as abnormal. If so recognised, these cancer cells will be destroyed by the immune system in the same way that bacteria and viruses are. However, cancer cells may sometimes escape detection by the immune system and hence the body’s own defence mechanism is not always adequate to get rid of cancer altogether. 
Today there are certain cancer treatments that tap into the immune system’s ability to fight cancer cells. Such treatments enhance the body’s ability to recognise and destroy cancer cells and include:
- Monoclonal antibodies (a monoclonal antibody is produced by cloning a unique white blood cell so that all subsequent antibodies derived this way can be traced back to a unique parent cell) – these antibodies recognise and attack certain proteins on cancer cells. 
- Cytokines (small proteins that are important in cell signalling) help boost the immune system – examples are interleukin and interferon. These cytokines may interfere with the way cancer cells grow and multiply, may stimulate certain white blood cells to attack cancer cells and can encourage cancer cells to produce chemicals that will attract immune system cells to them. [1,4]
- Vaccines for people with cancer to help the immune system recognise and attack cancer cells – are mainly available as part of clinical trials. [1,4]
- CAR T-cell therapy, also known as adoptive cell transfer, changes the genes in a person’s white blood cells that may be of help to some children with leukaemia and some adults with lymphoma. [1,5]
Maintaining a healthy immune system while coping with cancerBack to top
Since the immune system plays such an important role in the fight against cancer, it is important to look after it and ensure that it functions optimally. While it may seem daunting to do so at first glance, it basically requires establishing some healthy habits. These include:
Getting enough sleep
There is scientific evidence to show that lack of sleep suppresses the immune system. It is therefore important to try and get at least 7 hours or more of uninterrupted sleep per night. This may be challenging because cancer is a diagnosis that causes a lot of stress. In addition, some cancer treatments may cause sleeplessness as a side effect. Those who regularly (night after night or most nights) struggle to sleep should speak to their treating doctor about the available treatment options to facilitate a healthy sleep pattern.6, It is also important to establish healthy sleeping habits, such as going to bed and waking up at the same time every day, not going to bed hungry or over-satiated, having a bedtime ritual, such as bathing or journaling every night, and keeping one’s bedroom quiet, cool, and dark. 
Eating a healthy diet
This may be challenging because many cancer treatments may cause loss of appetite, nausea, or vomiting. The importance of a healthy, well-balanced diet to maintain a healthy immune system remains indisputable, however.6 A healthy diet includes a variety of foods, including fruits, vegetables, and proteins that provide the nutrients necessary to maintain one’s health, to feel good and to have energy. Talk to your oncology team or nutritionist if you are struggling with food choices and/or if you are concerned that your diet may be lacking in essential components. 
Getting regular exercise
It has been well established that moderate amounts of exercise have positive effects on the immune system. [6,7] If you have never exercised before or if you have not exercised in a long time, it may be quite daunting to start with an exercise program while receiving or recovering from cancer treatment. Remember that Rome was not built in a day. The best is to discuss an exercise program with your oncology team who will be able to assist you with enlisting the help of a physiotherapist, biokineticist, or exercise trainer with experience in dealing with cancer patients. Exercising in a group, such as walking activities two or three times a week, may help with adherence.
Get an outlet for stress
As mentioned above, the adrenal glands produce corticosteroids (and adrenalin) in response to stress. High levels of stress hormones (such as adrenaline and cortisol) over long periods of time suppress the immune system. This is the reason why many cancer clinics and hospitals have begun to refer patients for stress reduction therapy along with standard cancer treatments such as chemotherapy and radiation. Stress reduction therapy can range from meditation, yoga, massage, support groups, and even hobbies (e.g., reading, listening to music) and other techniques that, while helping to bring one’s stress levels down, will keep the immune system functioning well. Your oncology team will be able to refer you to a stress reduction therapy of choice.
Stay away from illness
Avoid contracting germs from others, so stay away from crowded places and steer clear of all contact with sick people. Cook food properly and wash vegetables and fruits before eating them. 
Use of supplements to boost the immune system
Eating a healthy diet is vitally important to maintain a well-functioning immune system. While dietary supplements may assist with obtaining the required amounts of vitamins and minerals and while some herbs and botanicals may be beneficial to cancer patients, it is important to keep in mind that no dietary supplement has been shown to treat or cure cancer. 
Patients receiving chemotherapy, radiotherapy or immunotherapy should ALWAYS discuss the use of health supplements with their treating doctor, as some supplements may interfere with the action of these therapies, either rendering them less effective or increasing their side effects.  It may be necessary to separate supplements from treatments for a couple of weeks or more. Your oncologist is in the best position to advise you.
ConclusionsBack to top
Cancer and its treatment may have detrimental effects on the body’s immune system thus compromising its ability to fend off infections and disease. On the other hand, the immune system plays a vital role in fighting cancer and thus certain anticancer therapies have been designed to bolster the ability of the immune system to recognise and destroy cancer cells.
Maintaining a healthy immune system while receiving cancer treatment or while recovering from it entails the establishment of healthy habits such as getting enough sleep, eating a healthy diet, getting enough exercise, and employing strategies to reduce stress.
Health supplements should be used only under the supervision of an oncologist or oncology treatment team.
- Cancer Research UK. 07 Jul 2020. The immune system and cancer. Cancer Research UK, viewed 30 Jun 2021, https://www.cancerresearchuk.org/about-cancer/what-is-cancer/body-systems-and-cancer/the-immune-system-and-cancer
- Cancer Treatment Centers of America. 08 May 2020. How do cancer treatments damage the immune system? CTCA, viewed 30 June 2021, https://www.cancercenter.com/community/blog/2020/05/covid-cancer-treatments-immune-system
- Lymphoma Info. 2020. Corticosteroids: Steroids in Cancer Treatment. Lymphoma Info, viewed 30 June 2021, https://www.lymphomainfo.net/articles/treatment/drugs-and-medication/steroids-in-cancer-treatment
- Cancer Research UK. 19 May 2021. Cytokines. Cancer Research UK, viewed 30 Jun 2021, https://www.cancerresearchuk.org/about-cancer/cancer-in-general/treatment/immunotherapy/types/cytokines
- Cancer Research UK. 20 Jan 2021. Types of cancer immunotherapy. Cancer Research UK, viewed 30 Jun 2021, https://www.cancerresearchuk.org/about-cancer/cancer-in-general/treatment/immunotherapy/types
- BreastCancer.Org. 10 May 2016. Taking care of your immune system. Breastcancer.org, viewed 30 June 2021, https://www.breastcancer.org/tips/immune/boost
- WebMD Cancer Centre. 5 Ways to boost your immunity during immunotherapy. WebMD, viewed 01 July 2021, https://www.webmd.com/cancer/cancer-treatment-protect-immune-system
- BreastCancer.Org. 18 November 2020. Suggestions for using supplements. Breastcancer.org, viewed 30 June 2021, https://www.breastcancer.org/tips/nutrition/supplements/suggestions
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