Immunotherapy is a type of treatment that helps the immune system fight cancer. To better understand it, it is important to understand how this system works: it acts to fight infections and other diseases that may eventually affect the body. It is also important in controlling cell growth and death. Some types of cancer are able to bypass the immune system by using a kind of “camouflage” in order not to be noticed, or by “turning off” the mechanisms responsible for identifying that there is something wrong with that cell.
Immunotherapy treatment provides tools for the immune system to see these abnormal cells and fight them more strongly. This is done through oral, injectable, or topical (ointment) medications that stimulate the production of cytokines (protein molecules that act against cancer cells). The prognosis is better in patients whose tumors are lined with immune cells called tumor-infiltrating lymphocytes (TILs).
Although the immune system can prevent or slow down cancer growth, cancer cells may have the ability to bypass it to avoid destruction. In some situations, they can:
- Suffer genetic changes that make them less visible to the immune system;
- Have proteins on their surface that disable the power of immune cells over them (form a protective layer); and
- Alter the normal cells around the tumor so that they interfere with the way the immune system responds to cancer cells.
Treatment may be daily, weekly, or monthly – the frequency depends on factors such as the type of cancer and its stage, the immunotherapy to be used, and how the body responds to it. Some types of immunotherapy are given in cycles, in the same way as chemotherapy, followed by a rest period for the body to recover and produce new healthy cells.
Types of immunotherapy
There are several types of immunotherapy used in cancer treatment. The main ones are:
- Checkpoint inhibitors: these are drugs that block immune checkpoints. One of the roles of the immune system is to attack normal and abnormal cells in the body. To do this, it uses checkpoints – or checkpoints – which are the control molecules of immune cells that need to be activated or deactivated in order to initiate a defense response. Cancer cells can use these checkpoints to avoid being attacked, which is why immunotherapy drugs target them. It can have adverse effects such as inflammatory tissue damage, diarrhea, colitis, skin rash, dermatitis, elevated transaminases, hypophysitis, and thyroiditis;
- Adoptive T-cell transfer: further enhances the natural ability of T-cells to fight cancer. In this approach, immune cells are removed from the tumor and the most active ones against the cancer are selected or altered in the laboratory to become even better at attacking the cancer cells – they are cultivated in large quantities and, when ready, transferred back to the body by intravenous injection. Once in the body, they begin to fight the diseased cells. Possible adverse effects are vitiligo and uveitis (in patients with melanoma) and hepatotoxicity (in those with renal carcinoma);
- Monoclonal antibodies: these are drugs that help the body identify cancer cells. The antibodies are produced in the laboratory to bind to a specific target on the tumor cells and can cause an immune response that destroys the cancerous ones and mark them, making it easier for the immune system to identify them. This technique can also be called targeted therapy. Fever, chills, weakness, headache, nausea, vomiting, diarrhea, reduced blood pressure, and skin rashes are some possible adverse effects;
- Vaccines: These act against cancer by boosting the immune system’s response to cancer cells. In general, they are produced from the patient’s own tumor cells or from substances collected from them. Their purpose is to treat existing cancers by strengthening the body’s natural defenses against the disease, but they can also be used to slow or stop the growth of cancer cells, reduce the size of tumors, prevent relapse of the disease, and eliminate cancer cells left over from other forms of treatment. It is important to clarify that these vaccines are different from those that prevent disease, as they have a treatment role, not a prevention role. They can trigger fever, chills, fatigue, back and joint pain, nausea, and headache; and
- Immune system modulators: These enhance the response of the patient’s immune system against cancer. Some of these agents affect specific parts of the immune system, while others affect the immune system more generally. Possible adverse effects include bone marrow suppression, hepatotoxicity, nephrotoxicity, neurotoxicity, hypertension, increased risk for infections, leukopenia, gastrointestinal dysfunction, and thrombocytopenia.
Applications of immunotherapy
The indication of immunotherapy is related to the type of tumor and the stage of treatment the patient is at. Some of the cancers that benefit from immunotherapy treatments are:
- Bladder cancer;
- Brain cancer
- Breast Cancer;
- Cervical and Ovarian Cancer
- Colorectal Cancer;
- Head and neck cancer;
- Renal cancer
- Liver cancer;
- Lung cancer;
- Leukemia
- Prostate Cancer;
- Skin Cancer; and
- Lymphoma.
