The role of the immune system
1. The immune system consists of a complex collection of cells and organs that protect the body from these foreign disease causing organisms, molecules and cells by preventing their entry into the body, or if they are already inside the tissues or blood, by detecting and destroying them.
2. Dangerous molecules that are already inside the body are eliminated by white blood cells, known as the soldiers of the immune system, which include macrophages, lymphocytes and specialised white blood cells (leukocytes), including B-cells, T-cells and natural killer (NK) cells.
Cancer immunotherapy
1. Unlike other cancer treatments such as chemotherapy or radiotherapy which aim to remove cancer cells, mmunotherapies for cancer are aimed at utilizing the body’s own immune response to destroy cancer cells.
2. Tumour cells may escape detection by the immune system (immune-evasion). Although cancer cells may be different to normal healthy cells and often express abnormal proteins (antigens) on their cell surface that can be recognised by immune cells, sometimes the expression of antigens is very low, or may change over time. Tumours produce chemicals that suppress the immune response aimed at them.
How cancer immunotherapy works
1. A biomarker is a measurable biological factor that can tell us about certain aspects of human health. In the context of cancer immunotherapy, biomarkers can provide insights into each patient’s individual cancer – its genetic makeup, its behaviour, and its interactions with the immune system – which doctors can then use to determine the approach most likely to benefit a particular person.
2. There are several types of cancer immunotherapy aimed at helping immune cells recognize cancer cells and increasing the efficiency of the anti-cancer immune response:
•Stimulating a non-specific anti-tumour response by administering cytokines, synthetic molecules or hormones. Cytokines are most commonly used. They regulate growth and development of immune cells, increasing the immune response against cancer cells.
• A nonspecific response can also be stimulated by injecting activated T cells into a person with cancer. Clinical trials of this type of therapy are ongoing.
• Vaccines that contain genetic material from tumours or viruses (some cancers are caused by a virus) can be administered to a person with cancer. By increasing the exposure of the immune cells to these antigens, the immune system mounts an attack on specific cancer cells bearing that antigen and retains a memory of that antigen for the future. Current vaccines are aimed at preventing cancer (Human Papillomavirus vaccine to prevent cervical cancer, hepatitis B vaccine) or its recurrence. Vaccines aimed at fighting existing cancers (including lung, prostate, bladder, colorectal, kidney and brain cancers) are in development.
• An immune response aimed at a single type of cancer cell can be stimulated by injecting antibodies that have already been activated with proteins from that tumour. The antibodies will bind exclusively to the tumour cells inside the body that bear this protein, initiating an immune response against that tumour specifically. In people with cancer, the use of monoclonal
antibodies improves survival and reduces the risk of recurrent cancer.
• Combinations of specific and non-specific immunotherapies may offer a promising new development in cancer immunotherapy.2
3. Immunotherapy has been shown to be a promising method for the treatment of certain malignant tumors including melanoma. It can effectively destroy tumour cells in the body, including metastases, but can also considerably reduce the risk of recurrence of the disease, as a result of the development of immunological memory.2
4. Immunotherapy is not for everyone. Some immunotherapy treatments are patient-specific and depend on the exact type of cancer the patient has. The patient’s doctor will need to determine their eligibility based on treatment criteria. It is important for the patient to discuss all available treatment options with their treating doctor to determine the best treatment for their specific diagnosis.3
Cancer statistics
1. There will be 18.1 million new cases of cancer and 9.6 million people will die with the disease worldwide in 2018.
2. According to the National Cancer Registry, over 70 000 new cases of cancer were diagnosed in 2014, making cancer a significant and growing problem for South Africa.
3. The number of new cases of cancer is expected to rise by about 70% to 22 million new cases per year during the next 20 years.
4. The most important risk factors for cancer are overweight and obesity, low fruit and vegetable intake, lack of physical activity, smoking, tobacco, and alcohol. These risk factors account for approximately one-third of cancer deaths.
5. Infections are important causes of cancer. Examples include viruses, such as HPV (cervical cancer), hepatitis B virus (liver cancer), human T-cell lymphotrophic leukaemia virus (leukaemia), human immunodeficiency virus (Kaposi’s sarcoma and non-Hodgkin lymphoma) and Epstein-Bar virus (lymphoma); bacteria and parasites.
6. In South African adults the most common hereditary cancers are breast and cervical cancer in women, prostate in men, and Kaposi’s sarcoma and colorectal cancer in both sexes.
References
1. Spiering MJ. Primer on the immune system. Reviews in Alcohol Research 2015; 37(2): 171-175.
2. Yuzhakova DV, Shirmanova MV, Sergeeva TF, et al. Immunotherapy of cancer. CTM 2016; 8(1): 173-181.
3. Understanding Cancer Immunotherapy. Second Edition. PRP Patient Resource Publishing. 2015: 14
4. National Health Laboratory Service. National Cancer Registry: cancer in South Africa, full reports: 2014.
5. Bray F, Ferlay J, Soerjomataram I, Siegel RL, Torre LA, Jemal A. Global cancer statistics 2018: GLOBOCAN
estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA: a cancer journal for
clinicians. 2018;68(6):394-424.
6. Cancer Association of South Africa (CANSA). Fact sheet on cancer. Available at:
http://www.cansa.org.za/files/2016/08/Fact-Sheet-Cancer-NCR-2011-web-Aug-2016.pdf. Accessed 28 January
2017.
