Immunotherapy, also known as targeted therapy or biotherapy, is a promising new cancer treatment that stimulates a patient's immune system so it is better able to fight disease. Children often receive immunotherapy in conjunction with more established cancer treatments, like chemotherapy and radiation.
Some types of immunotherapy are approved for use in children, but many others are still considered experimental and only offered to those who are enrolled in research studies (clinical trials). So far, results have been favorable, and researchers are confident that this emerging field of medicine will offer a new line of defense in the fight against cancer.
How the Immune System Works
The immune system is the body's defense against infectious organisms and other invaders. Through a series of steps called the immune response, the immune system attacks organisms and substances that invade our systems and cause disease. The immune system is made up of a network of cells, tissues, and organs that work together to protect the body.
The cells that are part of this defense system are white blood cells, or leukocytes. Leukocytes are produced or stored in many locations throughout the body, including the thymus, spleen, and bone marrow. For this reason, they are called the lymphoid organs. There are also clumps of lymphoid tissue throughout the body, primarily in the form of lymph nodes that house the leukocytes.
The leukocytes circulate through the body between the organs and nodes by means of the lymphatic vessels and blood vessels. In this way, the immune system works in a coordinated manner to monitor the body for germs or substances that might cause problems.
How Cancer (and Treatment) Can Affect Immunity
Immunodeficiencies occur when part of the immune system is not working properly or at all. Certain types of cancers that affect the immune system, like leukemia (cancer of the leukocytes) and lymphoma (cancer of the lymphatic tissues). These cancers weaken the immune system and make it harder for the body to fight off infection.
Some medicines given for cancer also may suppress the immune system. For example, while chemotherapy and radiation destroy cancer cells, they can sometimes damage healthy cells, too — including those found in the bone marrow and other parts of the immune system.
Many kids who undergo chemotherapy and/or radiation temporarily lose bacteria-fighting leukocytes, called neutrophils. When neutrophil counts are low, it's hard for kids to fight infection (this is called neutropenia).
Types of Immunotherapy
The aim of immunotherapy is to boost the immune system through the use of:
- active therapies, which help stimulate immune system responses already present in the body
- passive therapies, which supplement a patient's immune system with cell proteins, often manmade, that help it to work harder
Several types of immunotherapies from these two classes currently are in use or being studied by researchers, including:
Monoclonal antibodies (MAbs or mAbs). Monoclonal antibodies, a passive therapy, are the most widely used form of immunotherapy. Special manmade antibodies (disease-fighting proteins) manufactured in a lab are introduced into the body to boost immune system function. These drugs typically end in "mab" (rituximab, alemtuzumab, etc.), and are routinely part of the treatment plan for many different types of cancers, such as non-Hodgkin lymphoma.
Cancer vaccines. Unlike vaccines for the flu or chickenpox, biologic cancer vaccines don't try to prevent disease. Instead they stimulate the immune system to launch an attack on cancer cells that are already in the body. Cancer cells spread because, for some reason, the immune system doesn't recognize them as foreign. So they are able to fly under the radar, so to speak, and their growth remains unchecked.
But cancer vaccines work on the premise that a person's immune system can be taught to recognize cancer cells and attack them. It can do this by being introduced to inactivated forms of these cells or to specific proteins that are unique to cancer cells.
Currently, cancer vaccines are only available via research studies for a limited group of patients with certain types of cancer.
Non-specific immunotherapies. Unlike cancer vaccines, which are very specific to certain cells, non-specific immunotherapies simply work to boost overall immune system function. They may be given alone, or as adjuvants (therapies used alongside other treatments to improve how they work). Some non-specific immunotherapies include cytokines, interleukins, and interferons, all of which are naturally occurring proteins that play a role in the immune system's response to disease. They can be used to help children who are experiencing neutropenia.
Like other cancer treatments, immunotherapy can cause side effects that occur during treatment or soon after. Side effects include flu-like symptoms such as fever, chills, headache, and increased tiredness or fatigue.
Although many doctors and researchers believe the field of immunotherapy holds great promise for fighting cancer, it's still too early to tell whether this area of medicine will forever change the way cancer is treated.
Many treatments have been proven safe and effective in short-term clinical studies but long-term risks, or late effects, are unknown. Still, many patients find that the benefits of therapy outweigh potential risks.
If you have questions about specific immunotherapies and whether they might benefit your child, talk to your doctor. Also ask whether your child might be eligible to participate in a clinical trial.