The immune system is an intricate combination of various organs distributed throughout the body. It helps the body to protect itself against invasion by germs, diseases and infections (see pic above).
When a germ enters the body, the white blood cells (lymphocytes) are triggered to attack it. White blood cells constantly move throughout the body via the immune system.
White blood cells consist of two types; B cells and T cells. Both types produce antibodies that destroy viruses and bacteria.
There is also a third type; the large phagocytes which surrounds the microbes that are invading the body, and swallows them. When the immune system is compromised, germs can easily enter the body and attack it.
Infections caused by microorganisms or germs that enter the body are a high risk for children with cancer that are undergoing treatment. The main types of germs that enter the body and multiply, causing illness or more harm to the body are viruses, protozoa (some of which act as parasites), bacteria, and fungal organisms.
Infections in those with cancer or who are undergoing treatment for cancer can be far more serious than the average individual, and can also be harder to treat. Those most at risk for infections are patients who have undergone surgery such as a bone marrow transplant or are receiving chemotherapy or radiation treatment.
This is why hospital wards in which these children stay while receiving treatments are highly sterile and visitors are kept to an absolute minimum.
Why Cancer Patients Have an Increased Risk of Infection
There are various reasons why cancer patients carry a higher risk of infection and need to be protected against it, especially while in hospital undergoing treatment.
Some types of cancer can damage the blood and immune systems or even change the way that they work. Hodgkin and non-Hodgkin Lymphomas and certain types of leukaemia begin in the cells in the immune system and alter the way the immune system works, making the same cells that used to protect the body now interfere with the normal way your immune system works.
There are many other types of cancer that also affect the immune system, but generally it is not the cancer itself, but the treatments that cause long or short-term damage to the immune system.
Surgery can cause long-term damage to the immune system and treatments like chemotherapy, radiation therapy, and immunotherapy usually affect the immune system short-term:
Most types of major surgery affect the immune system. Anaesthesia may play a role in this suppression of the immune system, as does the fact that surgery breaks the skin, damages mucous membrane and exposes internal tissues to germs. Add to this the incision that is made, and there is a great chance of infection.
Chemotherapy is one of the most common causes of a weakened immune system, which is what makes cancer patients high-risk for infections. Some chemo drugs affect the immune system more than others, and can affect the way the body makes red and white blood cells and platelets; white blood cells are generally the most affected by chemotherapy.
The type and severity of the infection depends on various factors:
• What the chemo dose is
• Which particular chemo drugs are used
• The type of cancer being treated
• How often chemo is administered
• Whether the patient has had treatment for cancer before
Radiation therapy can cause a low white blood cell count, which increases the risk for infection. Similarly to chemotherapy treatment, the amount that the immune system is affected by radiation depends on certain factors:
• How much of the body is being treated by radiation
• Which part of the body is being treated by radiation
• The total dose of radiation given
• How often radiation is given
Immunotherapy or biotherapy is given to make the immune system stronger and better able to attack cancer cells. It is either used as a treatment on its own or together with another type of treatment.
Unfortunately immunotherapy treatment sometimes changes the way that the patient’s immune system works, and this puts these individuals at high risk for immune suppression. Some of the immunotherapy drugs lower the levels of all white blood cells and some only lower the levels of lymphocytes. Low lymphocyte levels increase the risk of contracting serious viral infections.
Hematopoietic Stem Cell Transplant
Hematopoietic stem cell transplant is the terminology used to include Umbilical Cord Blood Stem Cell Transplant (UCBSCT), Peripheral Blood Stem Cell Transplant (PBSCT), and Bone Marrow Transplant (BMT). These are all cancer treatments that can make use of very high doses of chemo and/or total body irradiation (TBI) to rid the body of cancer cells.
The process unfortunately also kills the blood-forming stem cells of the patient’s normal bone marrow. Because of this, stem cells are either removed from the patient and saved before the high-dose chemo is given or donor stem cells are used to replace those that were lost during treatment. Once the treatment is completed and these stem cells are replaced, which enables new blood cells to be made and the immune system to be restored.
Sometimes high-dose chemo is used together with total body irradiation for transplants, creating a suppressed immune system that can last for far longer.
Strict measures are used to protect patients from infections:
• Keeping transplant patients secluded until their white blood cell counts reach normal
• Monitoring the patient closely for signs of infection and treating quickly if any are found
• Limiting the patient’s exposure to other sources of germs and other people
So remember, the next time that you want to visit a child with cancer in the hospital, do not be offended or hurt when told it is not possible.
Remember, the most important thing here is the health and recuperation of the child.