Immunotherapy for Cancer
Immunotherapy is used to stimulate the body's immune system against cancer. These treatments target specific genetic characteristics of the tumor cells. The genetic characteristics of tumors do not depend on what organ in the body the cancer develops. So these drugs may be effective against many types of cancer. (See also Cancer Treatment Principles.)
There are several different types of treatments that doctors use to stimulate the immune system. And this area of cancer treatment is being intensively studied. The National Cancer Institute maintains an up-to-date list of immunotherapy drugs (as well as other drugs used to treat cancer). The list provides a brief summary of each drug's uses and links to additional information.
Monoclonal antibody therapy involves the use of experimentally produced antibodies to target specific proteins on the surface of cancer cells. There are many such antibodies available, and others are currently being studied. Trastuzumab is one such antibody, which attacks the HER-2/neu receptor present on the surface of cancer cells in 25% of women with breast cancer. Trastuzumab enhances the effect of chemotherapy drugs.
Rituximab is highly effective in treating lymphomas and chronic lymphocytic leukemia. Rituximab linked to a radioactive isotope can be used to deliver radiation directly to lymphoma cells.
Gemtuzumab ozogamicin, a combined antibody and drug, is effective in some people with acute myeloid leukemia.
Several monoclonal antibodies modify the function of immune checkpoints, which help to control the immune system, and in so doing stimulate the body's natural anticancer immunity. Drugs called checkpoint inhibitors may block checkpoints CTLA-4 (ipilimumab) and PD1 or PD-L1 (nivolumab, pembrolizumab, durvalumab, atezolizumab, avelumab). Pembrolizumab can be used for any advanced cancer with a DNA-repair defect independent of where the cancer is in the body. These drugs are sometimes given alone or combined with other anticancer drugs.
Biologic response modifiers stimulate normal cells to produce chemical messengers (mediators) that improve the immune system's ability to find and destroy cancer cells.
Interferon (of which there are several types) is the best-known and most widely used biologic response modifier. Almost all human cells produce interferon naturally, but interferon can also be made through biotechnology. Although its precise mechanisms of action are not totally clear, interferon has a role in the treatment of several cancers, such as Kaposi sarcoma and malignant melanoma.
Interleukins are messengers produced by certain immune system cells (activated T cells). Giving interleukins can help in the treatment of metastatic melanoma and may be of benefit in kidney cancer. Interleukin 2, which is produced by certain white blood cells, can be helpful in renal cell carcinoma and metastatic melanoma.
Cancer cells are immature and grow rapidly, so one type of drug promotes the more rapid maturation (differentiation) of cancer cells to slow the growth of the tumor. These differentiating drugs may only be effective for a short time, so they are often used in combination chemotherapy.
Antiangiogenesis drugs prevent the tumor from forming new blood vessels. If blood vessel growth is prevented, the cancer will lack the blood flow necessary to grow and expand.
Still other drugs target the pathways cancer cells use to signal additional cells to form or grow.
Vaccines composed of material derived from cancer cells can boost the body's production of antibodies or immune cells that can attack the cancer. Extracts of weakened tuberculosis bacteria, which are known to boost the immune response, have been successful when instilled into the bladder to prevent recurrence of bladder tumors.
Because changes (mutations) of genes cause cancer, researchers are looking at ways to manipulate genes to fight cancer. A newer, advanced form of gene therapy involves genetically modifying T cells (a type of immune cell). Doctors remove T cells from a person's blood and genetically modify them to recognize that person's specific cancer. When the modified T cells, called chimeric antigen receptor cells or CAR-T-cells, are put back in the person's bloodstream, they attack the cancer. Recently, two CAR-T-cell therapies became available. This technique is used in people with acute lymphoblastic leukemia or lymphoma.
Stem cells are unspecialized cells that have the capability to become many different types of cells. Stem cells in the bone marrow are the source of all the different normal blood cells. High doses of chemotherapy drugs or radiation therapy can kill cancer cells but often also kills the person's stem cells, which prevents the bone marrow from producing normal blood cells. Stem cell transplantation replaces the killed stem cells with healthy stem cells from a donor. Donors can be the person with cancer (an autotransplant) or another genetically matched related or unrelated person (an allotransplant). Stem cell transplants allow doctors to give high doses of chemotherapy to treat leukemias and some lymphomas.