Immunotherapy is a type of treatment that helps the patient’s own immune system fight cancer. To understand it, it is important to understand how this system works: it acts to combat infections and other diseases that may affect the body. It is also important for controlling the growth and death of cells that have “defects” that make them a threat. Some types of cancer are able to evade the immune system by using a kind of “camouflage” to go unnoticed or by “turning off” the mechanisms responsible for identifying genetic errors in that cell.
Although the immune system can prevent or slow down cancer growth – and in fact, it is estimated that this process occurs naturally imperceptibly all the time – cancer cells can evade it. In some situations, they can:
- Undergo genetic alterations that make them less visible to the immune system;
- Have proteins on their surface that disable the immune cells’ power over them (forming a protective layer);
- Alter the normal cells around the tumor to interfere with how the immune system responds to cancer cells.
Immunotherapy “wakes up” the immune system so that it can see these abnormal cells and fight them in a targeted way. This is done through intravenous medications that make some tumor targets more “visible” to the immune system.
Treatment can 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 done in cycles, similar to chemotherapy. Although the frequency of adverse events is much lower compared to chemotherapy, occasional periods of treatment “rest” may be necessary.
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 medications (ointments) that stimulate the production of cytokines (protein molecules that act against cancer cells). The prognosis is better in patients whose tumors have a lining of immune cells called tumor-infiltrating lymphocytes (TIL).
Although the immune system can prevent or slow down cancer growth, cancer cells can evade it to avoid destruction. In some situations, they can:
- Undergo genetic changes that make them less visible to the immune system;
- Have proteins on their surface that disable the power of immune cells against them (forming a protective layer); and
- Alter normal cells around the tumor to interfere with how the immune system responds to cancer cells.
The 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 done in cycles, similar to chemotherapy, followed by a rest period for the body to recover and produce new healthy cells.
Types of immunotherapies
Existem diversos tipos de imunoterapia utilizados no tratamento oncológico. Os principais são:
Checkpoint inhibitors: One of the roles of the immune system is to attack abnormal or foreign cells or components in the body. To do this without attacking normal cells, the immune system uses “checkpoints.” Checkpoints are molecules present in normal tissues that, when found by immune cells, inhibit their action, thus avoiding the destruction of healthy cells. Cancer cells can use some of these checkpoints to evade the immune system. Immunotherapy blocks some of these checkpoints, removing the inhibition of the immune system against them, and thus allowing the immune activity against certain elements present in tumor development. This is the most commonly used type of immunotherapy currently. Although rare, it can have side effects such as inflammatory tissue damage, diarrhea, colitis, skin rash, dermatitis, elevated transaminases, hypophysitis, and thyroiditis.
Adoptive T cell transfer: This approach further enhances the natural ability of T cells (a specific type of immune system component) to fight cancer. In this approach, immune cells present in the tumor are isolated, and those most active against cancer are selected or altered in the laboratory to become even more effective in attacking tumor cells. They are then cultured in large quantities and, when ready, transferred back to the body through intravenous injection. Once in the body, they begin to fight tumor cells. Possible side effects are vitiligo and uveitis (in patients with melanoma) and hepatotoxicity (in those with renal carcinoma).
Monoclonal antibodies: These antibodies are produced in the laboratory to bind to a specific target on tumor cells and can either provoke an immune response that destroys them or simply mark them as targets, making it easier for the immune system to identify them. This technique falls under targeted therapy. Fever, chills, weakness, headache, nausea, vomiting, diarrhea, reduced blood pressure, and rashes are some possible side effects.
Vaccines: These vaccines work against cancer by boosting the immune system’s response to cancer cells. They are generally made from the patient’s own tumor cells or substances extracted from them. Their aim is to treat existing cancers by strengthening the body’s natural defenses against the disease, but they can also be used to slow or prevent the growth of new tumors and recurrences. It is important to clarify that these vaccines are different from those that prevent diseases, as they have a treatment role, not a preventive one. They can trigger fever, chills, fatigue, back and joint pain, nausea, and headaches.
Immune system modulators: These agents increase the patient’s immune system response against cancer. Some of these agents affect specific parts of the immune system, while others target it more generally. Potential side effects include suppression of blood cell production by the bone marrow, hepatotoxicity, nephrotoxicity, neurotoxicity, hypertension, increased risk of infections, leukopenia, gastrointestinal dysfunction, and thrombocytopenia.
Applications of immunotherapy
The indication for immunotherapy is related to the type of tumor and the stage of treatment the patient is in. Some of the cancers that currently benefit most from immunotherapeutic treatments are:
- Bladder cancer;
- Breast cancer;
- Head and neck cancer;
- Kidney cancer;
- Liver cancer;
- Lung cancer;
- Leukemia;
- Skin cancer;
- Lymphoma.
Immunotherapy side effects
While often well tolerated, immunotherapy can have some side effects. These effects can vary depending on the type of immunotherapy used and the patient’s immune system response to treatment. In some cases, reactions may include:
- Weight gain or loss
- Hair loss
- Feeling cold
- Excessive fatigue, among others.
However, studies are ongoing evaluating the use of immunotherapy for virtually all types of tumors.
