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What types of cancer treatment exist?
What is chemotherapy?
What is radiation therapy?
What is biological or immune therapy?
What is cancer vaccine therapy?
What is cryotherapy?
What are clinical trials?
What types of cancer treatment exist?
When you or someone in your family is first diagnosed with cancer, you face an overwhelming number of decisions. The choice of a treatment option alone may be literally a matter of life and death. Take some time to familiarize yourself with some of the treatments you may be offered. There are "classic" treatments, such as chemotherapy and radiation therapy. But there are also new, groundbreaking treatments, such as cancer vaccines, immunotherapy and others.
What is chemotherapy?
Chemotherapy, the use of drugs to destroy cancer cells, is a form of systemic treatment. It goes wherever the bloodstream carries it. It will affect cells and organs all over your body. In addition to the site of the original (primary) tumor, it also will attempt to kill cancer cells that may have spread (metastasized) from the primary site to distant organs and tissues.
Chemotherapy works because cancer cells grow more quickly than normal cells. During growth periods, the cell is the weakest. But some normal cells, such as hair and the intestinal lining, also grow rapidly and also may be damaged by chemotherapy. That's why some of the side effects of chemotherapy include nausea, diarrhea or constipation, and hair loss.
When you talk with your doctor about chemotherapy, you will learn there are different types of drug actions that affect the tumor cells in different ways, either to prevent cell division (cyclophosphamide and doxorubicin), starve the cancer cells (5-fluorouracil), or even paralyze them (vincristine). Certain hormones and hormone-substitutes are also used as hormonal therapy to complement chemotherapy (tamoxifen).
You may receive a single drug or two to five drugs in combination therapy. Combinations are used to improve the chances of destroying cancer cells at different points in their life cycles.
Chemotherapy can be used for different goals, depending on the type of cancer and how advanced it is. Those goals are to:
- Cure the cancer. Cures occur when you have no evidence of cancer cells in your body after a certain amount of time. Chemotherapy given after surgery (adjuvant chemotherapy) is done to try to decrease the recurrence of the cancer.
- Control the cancer. Sometimes, chemotherapy can slow or stop the spread of cancer. Or, it can kill cancer cells that have spread to other parts of the body.
- Palliation. Relieve symptoms caused by the cancer's size. Pain can be relieved or breathing eased by using chemotherapy to improve quality of life.
- Shrink a tumor before surgery or radiation therapy (neoadjuvant chemotherapy).
What is radiation therapy?
Speed of cell division also makes cancer cells more sensitive to radiation. Radiation can come from a source outside the body (external beam radiation) as either a low- or high-energy beam. Radiation sources can also be placed inside the body (internal, or brachytherapy), using small seeds or beads of radioactive material placed in or around the tumor area.
The fact that radiation therapy, or RT, is applied as close to the tumor as possible makes RT a form of localized treatment. Certain cancers, such as leukemia, lymphoma, skin cancer, and many reproductive organ cancers often are treated with RT. Also, solid tumors with good blood and oxygen supplies can be treated using RT. If you have a tumor that is not very well supplied with blood and oxygen, higher doses of radiation may be required to kill those cells. Partial doses of external RT are usually spread over a certain period of time, until the complete dose is given. This allows normal cells to recover, without allowing cancer cells to divide.
Other, less frequently used methods of RT include intraoperative radiotherapy (IORT) and stereotactic radiation. Intraoperative radiotherapy works by targeting strong doses of radiation directly into or next to the tumor during surgery. It reduces harm to nearby tissues, and kills cancer cells that might have been left after a tumor is removed. Stereotactic RT uses computers to aim several beams of radiation from different angles onto a tumor at the same time. For example, 3-D conformal radiotherapy used for prostate cancer.
Experimental areas for RT are exploring higher energy beams, as high linear energy transfer (high LET) therapy, to pack more energy into a dose of radiation. Radiosensitizing drugs make tumor cells more sensitive to radiation. Radioprotectors are chemicals that protect normal cells from radiation effects. Hyperthermia, which is increased temperature, is also being studied as a way to increase the sensitivity of tissues.
Newer methods of local "spot" reduction for small brain or body tumors include Gamma Knife® and CyberKnife® research methods to help deliver a small focal field. These devices are available at a few large cancer centers.
Despite its name, the Gamma Knife isn't a knife. Rather, it's a single, finely focused, high dose of radiation precisely targeting the tumor with little or no damage to surrounding tissue.
The CyberKnife is a painless, non-invasive therapy that delivers high doses of precisely targeted radiation to destroy tumors or lesions within the body. A robotic arm delivers highly focused beams of radiation. The flexibility of the robotic arm makes it possible to treat areas such as the spine and spinal cord that cannot be treated by other radiosurgery techniques.
What is biological or immune therapy?
This type of therapy uses drugs or vaccines, immunotherapy and monoclonal antibodies to boost your immune system in its fight against cancer. Since the human body is capable of making these materials in small amounts to fight cancer, additional amounts, made in the laboratory and given to patients, may destroy their cancer cells. Immune boosters also stimulate the body to repair tissues or make new healthy cells after chemotherapy.
There are several types of immune therapy:
- Nonspecific immunomodulating agents
- Interferons (IFN)
- Interleukins (IL)
- Colony-stimulating factors (CSFs)
- Monoclonal antibodies (MOABs)- Avastin® (bevacizumab), Erbitux (Cetuximab)
- Tyrosine kinase inhibitors - Tarceva® (erlotinib), and Gleevec® (imatinib mesylate)
- Cancer vaccines
What are nonspecific immunomodulating agents?
These substances can stimulate the immune system to increase the production of invasion-fighting blood cells and chemicals. One of the agents for cancer treatment is bacillus Calmette-Guerin (BCG).
Even though BCG was developed as a vaccine against tuberculosis, it is also used to treat superficial bladder cancer after surgery to prevent recurrences. BCG solution is held in the bladder for a short time, and then emptied during urination.
What are biological response modifiers?
These agents, which continue to be developed in laboratories, help your body change the way it interacts with cancer cells. The biological response modifiers (BRMs) include interferons, interleukins, colony-stimulating factors, monoclonal antibodies and vaccines.
The BRMs have different roles but are used to:
- Stop, control or slow the process of cancer growth
- Make cancer cells more easily destroyed by the immune system
- Boost the immune system cells (T cells, natural killer (NK) cells, and macrophages (big eater cells)) to destroy cancer cells
- Change the growth pattern of cancer cells to function more naturally
- Block or reverse the changes in a normal cell that makes it cancerous
The activities of BRMs also include improving the body's repair and replacement abilities after normal cells have been damaged or destroyed by treatments, and prevent cancer cells from spreading. The modifiers are usually combined with each other, or with other treatments, such as chemotherapy and RT. They have side effects, which vary from patient to patient. These effects include, rashes at the site of injection, flu-like symptoms with fever, chills, nausea, vomiting, and loss of appetite. Fatigue, bone pain, and serious allergic reactions may also appear.
Interferons
Interferons (IFN) are cytokines, proteins that can act on a cell's function or growth processes. If you are a candidate for interferon, it works to improve your body's reaction to cancer cells. Interferons can act directly on cancer cells and slow their growth. Some IFNs can change a precancerous cell growth process and make it more normal. They also boost T-cell and NK cell lymphocyte functioning and macrophage cell function. They are approved for use in the treatment of certain cancers. Some of their cancer applications include hairy cell leukemia, melanoma, chronic myeloid leukemia, and AIDS-related Kaposi's sarcoma. Clinical research regarding IFNs is also being conducted in the treatment of metastatic kidney cancer and non-Hodgkin's lymphoma.
Interleukins
Another cytokine group, the interleukins (IL) also occur naturally in the body and are reproduced in the laboratory. Interleukin-2 (IL-2) is the most widely studied, and is found to stimulate the growth and activity of many of the immune system cells, specifically lymphocytes, that have "killer" function. IL-2 has been approved for metastatic kidney cancer and metastatic melanoma, and under investigation for colorectal, ovarian, lung, brain, breast, prostate, and some of the leukemias and lymphomas.
Colony-stimulating factors
Colony-stimulating factors (CSF) stimulate the bone marrow to produce larger populations of red and white blood cells and platelets, after RT or chemotherapy have affected the bone marrow. They allow doctors to increase doses of chemotherapy drugs, because they know the bone marrow will be producing large amounts of cells needed to fight any infections, avoid anemia, and reduce bleeding tendencies.
- G-CSF and GM-CSF improve the white blood cell counts and stem cell production if you are a candidate for stem cell or bone marrow transplantation.
- Erythropoietin stimulates red blood cell production to help avoid anemia and the need for transfusion during chemotherapy.
- Oprelvekin is a platelet booster, and may help you avoid platelet transfusions if you are receiving high-dose chemotherapy.
- New drugs for stimulating platelet production are in research development.
Colony-stimulating factors are being studied for the treatment of some leukemias, metastatic colorectal cancer, melanoma, lung cancer and other types of cancer.
Monoclonal antibodies
Specifically designed to seek out and destroy their cancer-counterpart antigens, monoclonal antibodies (MOAB) attack the same way our other antibodies attack and destroy disease particles or bacteria that enter our bodies. If researchers are able to find a specific antigen in a cancer, they may be able to grow a specific single-cloned (monoclonal) antibody to try and attack the cancer and slow it down or destroy it. One of the more interesting uses of an MOAB is to attach a poison or small dose of radiation to it. Then, when sent to the cancer "match," the MOAB brings in its poison or radiation to help destroy the cancer cells. Sometimes, MOABs are used to destroy any cancer cells in a bone marrow sample being used for transplantation later.
FDA-approved MOABs are rituximab (Rituxan®) and trastuzumab (Herceptin®) for the treatment of B-cell non-Hodgkin's lymphoma and breast cancer. Bevacizumab (Avastin) and cetuximab (Erbitux) are approved for the treatment of colon cancer. Research is ongoing for the application of MOABs to additional types of cancer. New MOABs are being studied to treat several cancers. Newly approved Zevelin® has an isotope added to Rituxan and gives specific local radiotherapy.
What is cancer vaccine therapy?
If you understand how vaccines work, you can understand how cancer vaccines can be used to treat certain types of cancer. Even though you may have received your vaccines to help prevent getting a disease or infection, cancer vaccines are a little different, because they are made to boost the immune response in the presence of cancer to try to treat it.
Like MOABs, cancer vaccines are specific to a type of cancer, and they are made from cancer cells themselves. They are given to help the body remember the cancer type and fight off any possible recurrence in the future. So, if you've had a cancer removed by surgery, the tissue may be able to become the basis of a vaccine, and when you receive the vaccine, it may prevent a recurrence of your tumor. Even if your cancer is small, and may not be operated on, tissue samples may provide enough material to make a vaccine.
What is cryotherapy?
Extreme cold (freezing) will destroy cancer cells, and cryosurgery with liquid nitrogen (minus 320.8 degrees F or minus 196 degrees C) has long been used to treat tumors on the surface of the body. With the development of the cryoprobe, a slender wand with a tip super-cooled with circulating liquid nitrogen, internal tumors can now be frozen as well. Live ultrasound pictures help to avoid damage to nearby healthy tissue and are used to monitor the location and placement of the probe.
While cryotherapy has been proven effective for cancers such as retinoblastoma (cancer of the retina), cancers of the skin and of the cervix, it is also being investigated for the treatment of prostate and liver cancers. It is a localized form of therapy.
What are clinical trials?
Human cancer treatment studies, or research studies, are tests of new treatments in people with cancer. Clinical trials involve many different ways of treatment and are constantly in progress or being started all over the world. Besides drugs, trials involve surgical techniques, immune therapies, and other treatment methods such as gene therapy. The goal of this research is to find better ways to treat cancer and help cancer patients. If your doctor does not suggest you take part in a clinical trial, you may want to ask. Clinical trials are being conducted for a variety of cancers, such as melanoma, lymphomas, kidney, breast, ovary, prostate, colon and rectum. For information, go to http://www.clinicaltrials.gov/.
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External Sources
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The National Cancer Institute.
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Dollinger M, Rosenbaum, EH, Tempero M., et al. Everyone's Guide to Cancer Therapy, Fourth Edition, Kansas City, Missouri: Andrews McMeel Publishing, 2002.
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This article was reviewed and updated June 2007.
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