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Cancer Treatment

There are three possible goals for cancer treatment:
  • Cure. Ideally, all cancer cells are killed or removed from the body and do not return.
  • Control. If cure is not possible, the goal of treatment is to control the disease in order to extend life while preserving its quality as much as possible.
  • Palliate. If the cancer is advanced, the main goal is to maintain quality of life without attempting to extend it.
In general, your doctor has five types of treatment from which to choose:

Surgery

Surgery is used to partially or completely remove a tumor. Surgery is most successful for solid tumors that are localized and have neither invaded the surrounding tissues or metastasized to distant sites. In addition to removing the tumor itself, a surgeon will remove a margin of normal tissue around the tumor and sometimes the lymph nodes that drain that region of the body.
The primary goal of surgery is the complete removal of the tumor. Unfortunately, in cases where the cancer has already spread, this may not be possible. Under these circumstances, surgeons may still remove a portion of the tumor, in a procedure known as debulking , in order to relieve symptoms or increase the effectiveness of other therapies, such as chemotherapy or radiation. To learn more about specific surgical procedures used to treat cancer, see the surgery treatment monograph .

Radiation

Radiation therapy is the use of high energy radiation to destroy cancer cells by irreparably damaging their DNA. In most cases, the radiation is repeatedly administered from a source outside of the body. Forms include:
  • External beam therapy, in which a beam of radiation from a treatment machine is directed to limited parts of the body to kill the primary tumor and/or to kill microscopic tumor deposits in the areas near the tumor, such as regional lymph nodes. Stereotactic radiosurgery is another method of delivering very highly directed high doses of radiation to a limited area in order to treat cancer and limit the injury to surrounding tissues.
  • Brachytherapy, in which radioactive material—sealed in a thin wire, catheter, or tube—is surgically placed directly into or near the tumor.
  • Intraoperative radiation therapy , which combines radiation and surgery. After the surgeon removes as much of the tumor as possible, a large dose of radiation is given directly to the tumor bed and nearby areas.
  • Photodynamic therapy (PDT), in which photosensitizers, or light-sensitive molecules, are injected into the bloodstream and absorbed by cells throughout the body, but preferentially cancer cells. Later, when the cancer cells are exposed to laser light, the photosensitizers are activated resulting in cell damage and death.
  • Hyperthermia, in which body tissues are exposed to high temperatures (up to 106 degrees F) in an effort to damage cancer cells and make those that survive more sensitive to the effects of radiation.
Like surgery, radiation therapy can sometimes be used for palliation (to relieve pain caused by a tumor). It is common, for example, to use radiation therapy to treat cancer that has metastasized to the spine, which is extremely painful and can result in fractures or spinal cord injuries. The radiation, however, is not expected to eliminate the cancer. To learn more about specific radiation therapies used to treat cancer, see the radiation treatment monograph.

Chemotherapy

Chemotherapy is the treatment of cancer with drugs that inhibit the growth of cancer cells. Two terms often used to describe chemotherapy are antineoplastic (meaning anticancer) and cytotoxic (cell-killing).
Chemotherapy is used to treat many cancers, either alone or in combination with other treatments. It differs from surgery or radiation in that it is almost always used as a systemic treatment, meaning the medication travels throughout the body via the bloodstream rather than being confined to one area. This makes chemotherapy the first choice for metastatic cancer since it can reach cancer cells that may have already spread throughout the body.
More than 100 drugs are currently used for chemotherapy—often in combination—and the list is constantly growing. These medications vary widely in their chemical composition, administration, indications, and side effects. Great care is generally needed when administering chemotherapy due to the severity of toxic and adverse reactions. To learn more about specific chemotherapy agents used to treat cancer, see the chemotherapy treatment monograph .

Biologic Therapies

In addition to locating and destroying the bacteria and viruses that make us sick, the immune system is responsible for seeking out and destroying cancer cells before they proliferate. If, for whatever reason, the immune system is unable to successfully clear the body of enemy cancer cells, it may still be possible to coax the system into battle. Scientists have developed a class of substances known as biologic response modifiers (BRM), which enhance the tumor-destroying capability of the immune system. One of several ways BRMs can accomplish this is by increasing the activity of chemical messengers ( cytokines ) that stimulate cytotoxic cells to fight. To learn more about specific biologic agents used to treat cancer, see the biologic therapies treatment monograph .

Hormonal Therapies

The growth of some tumors is stimulated by the presence of hormones. Hormonal therapies block the hormone receptors of certain cancer cells, discouraging them from proliferating. The anti-estrogen drug tamoxifen is the best example of an effective hormonal therapy for breast cancer. Similarly, chemical or surgical castration may be used to treat prostate cancer, another hormone-responsive tumor. Like chemotherapy, hormonal therapies are administered systemically, but are generally better tolerated. To learn more about specific hormonal agents used to treat cancer, see the hormonal therapies treatment monograph .

Assessing Treatment Effectiveness

The success of cancer treatment can be measured in several ways:
  • Response rates
  • Survival rates
  • Dose-limiting toxicities
Response rates (also called remission rates) indicate the percentage of patients whose disease goes into remission after treatment. Response rates can be either partial or complete. A partial response rate indicates a 50% reduction in the size of the primary tumor and no new areas of cancer. A complete response rate is the absence of detectable cancer. Response rates are generally used to describe chemotherapy and hormonal treatments rather than surgery or radiation.
Survival rates are expressed as the percentage of patients alive after a designated period of time. In cancer, it is common to measure 5-year-survival rates, which represent the number of people with cancer who are still alive five years after diagnosis, irrespective of whether or not their cancer persists at that time.
While five-year survival rates are often used to express the effectiveness of treatments, they say nothing about the number of people who are cured permanently of their cancer. They also should not be used to predict an individual patient’s prognosis. Five-year survival rates do not necessarily reflect current advances in the treatment of cancer, and they do not always take into account a number of individual factors that can influence survival, such as detection methods, treatment protocols, concurrent illnesses, tumor stage at diagnosis, or personal behaviors, all of which can influence survival rates.
Dose-limiting toxicities are severe adverse effects that preclude the use of higher, more effective doses of chemotherapy or radiotherapy. For example, the maximum dose of chemotherapy is restricted by the toxic effect it has on bone marrow ( myelosuppression ) .

References

American Cancer Society. Cancer Facts & Figures 2003 . Atlanta, GA: American Cancer Society, Inc;2003.

Bast RC, Kufe DW, Pollock RE, et al. Eds. Cancer Medicine . 5th ed. Hamilton, ON: Decker Inc; 2000.

Cancer. Merck Manual of Medical Information website. Available at: http://www.merck.com/mrkshared/mmanual%5Fhome/contents.jsp . Accessed March 25, 2003.

Defining cancer. National Cancer Institute website. Available at: http://www.cancer.gov/cancertopics/what-is-cancer . Accessed August 1, 2008.

Detailed guide. American Cancer Society website. Available at: http://www.cancer.org/ . Accessed August 1, 2008.

Finley RS, Balmer C. Concepts in Oncology Therapeutics . 2nd ed. Bethesda, MD: American Society of Health-System Pharmacists;1998.

Fox SI. Human Physiology . 4th ed. Dubuque, IA: William C. Brown Publishers;1993.

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