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Chemotherapy and Other Systemic Cancer Treatments


Robert Peter Gale

, MD, PhD, DSC(hc), Imperial College London

Last full review/revision Sep 2022| Content last modified Sep 2022
Topic Resources

Systemic treatments are those that have effects throughout the body rather than being applied directly to the cancer. Chemotherapy is a form of systemic treatment that uses drugs to kill cancer cells or to stop them from growing.

Systemic cancer therapy includes

  • Hormonal therapy

  • Chemotherapy (anti-cancer drugs)

  • Targeted drug therapy

  • Immune therapy

  • Gene therapy

  • Various other drugs for cancer

Immunotherapy is a systemic cancer treatment that stimulates the body's immune system Overview of the Immune System against cancer (see Immunotherapy for Cancer Immunotherapy for Cancer ).

The number of approved cancer therapies is increasing rapidly. The National Cancer Institute maintains an up-to-date list of drugs used to treat cancer. The list provides a brief summary of each drug's uses and links to additional information.

Not all cancers respond to chemotherapy. The type of cancer determines which drugs are used, in what combination, and at what dose and schedule. Chemotherapy may be used as the sole treatment or combined with radiation therapy Radiation Therapy for Cancer , surgery Surgery for Cancer , or immune therapy (see also Cancer Treatment Principles Cancer Treatment Principles ).

Hormonal Therapy for Cancer

Hormones are proteins produced by endocrine glands Endocrine Glands that affect activities of target tissues and organs. Hormones serve as messengers, controlling and coordinating activities throughout the body. Some cancers grow and spread more when they are exposed to certain hormones. Consequently, reversing the effects of these hormones may control some hormone-dependent cancers. However, these drugs also can cause symptoms of hormone deficiency.

For example, prostate cancer Prostate Cancer Prostate Cancer grows faster when exposed to the male sex hormone testosterone and other androgenic steroids. Thus, anti-androgen therapy is commonly used to treat prostate cancer. Some anti-androgen drugs, such as leuprolide, goserelin, and others, prevent the pituitary gland Overview of the Pituitary Gland from stimulating the testes to make testosterone. Other hormonal therapy drugs, such as flutamide, bicalutamide, and nilutamide, are used to block the effects of testosterone. These hormonal therapy drugs do not cure prostate cancer, but they can slow the growth and spread of prostate cancer. However, these drugs also may cause symptoms of testosterone deficiency, such as hot flashes, osteoporosis, loss of energy, reduction in muscle mass, fluid weight gain, reduction of libido, decrease in body hair, erectile dysfunction, and breast enlargement.

Some breast cancers Breast Cancer Breast Cancer grow faster when exposed to the female sex hormones estrogen and/or progesterone. Drugs such as tamoxifen and raloxifene bind to estrogen receptors and inhibit the growth of breast cancers with estrogen receptors. These drugs also reduce the risk of developing breast cancer. Aromatase inhibitors, such as anastrozole, reduce the production of estrogen and have a similar benefit.

Hormonal therapy may be used alone or combined with other types of cancer therapy.


Chemotherapy involves the use of drugs to destroy cancer cells. Although an ideal drug would destroy cancer cells without harming normal cells, most drugs are not that selective. Instead, drugs are designed to inflict greater damage on cancer cells than on normal cells, typically by using drugs that affect a cell's ability to grow. Uncontrolled and rapid growth is characteristic of cancer cells. However, because normal cells also need to grow, and some grow quite rapidly (such as those in the bone marrow and those lining the mouth and intestine), all chemotherapy drugs affect normal cells and cause side effects.

Chemotherapy is used to cure cancer. It may also decrease the chance that cancer will return, slow the growth of a cancer, or shrink tumors that are causing pain or other problems.

Although a single chemotherapy drug may be effective against some types of cancer, often doctors give several chemotherapy drugs at the same time (combination chemotherapy Combination Cancer Therapy ).

High-dose chemotherapy

In an attempt to increase the tumor-destroying effects of cancer drugs, the dose may be increased. Sometimes the rest period between cycles of chemotherapy may be decreased. High-dose chemotherapy, with shortened rest periods, is routinely used in many cancers such as leukemias, lymphomas, lung cancers, pancreas cancers, digestive system cancers, breast cancers, and others.

High-dose chemotherapy is sometimes used to treat people whose cancer has recurred after standard-dose chemotherapy, particularly for people with myeloma, lymphoma, and leukemia. However, high-dose chemotherapy can cause life-threatening injury to the bone marrow. Therefore, high-dose chemotherapy is commonly combined with strategies to protect the bone marrow (rescue). In bone marrow rescue, bone marrow cells are harvested before the chemotherapy and returned to the person after chemotherapy. In some cases these cells can be isolated from the bloodstream rather than from the bone marrow and can be infused back into the person after chemotherapy to restore bone marrow function.

Targeted Drugs

One approach to increase efficacy uses drugs that target specific mutations in cancer cells. These drugs control cancer cells by targeting specific pathways and processes vital to the cancer cells’ growth and survival Imatinib and other drugs that inhibit the enzyme tyrosine kinase,are highly effective in chronic myeloid leukemia Chronic Myeloid Leukemia (CML) and certain cancers of the digestive tract. Erlotinib, gefitinib, and osimertinib target mutations in the epidermal growth factor receptor (EGFR) and are used to treat lung cancers with this mutation. Molecularly targeted drugs have proven useful in treating many other cancers, including other leukemias, and breast and kidney cancers.

Gene Therapy

Because changes (mutations) of genes cause cancer, researchers are looking at ways to manipulate genes to fight cancer.

One form of gene therapy involves genetically modifying T cells T cells One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more T cells (a type of immune cell)—see also Modified T cells T cells One of the body's lines of defense ( immune system) involves white blood cells (leukocytes) that travel through the bloodstream and into tissues, searching for and attacking microorganisms and... read more T cells . 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. CAR-T-cells can be used in people with acute lymphoblastic leukemia, multiple myeloma, and lymphoma.

New, still-experimental, techniques allow scientists to insert new genes into a cells, switch off abnormal genes, or increase the activity of helpful genes (see also Gene Therapy Gene Therapy ). Doctors hope these techniques may one day be useful for treating cancer.

Other Drugs

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 Combination Cancer Therapy . Acute

Anti-angiogenesis drugs prevent a tumor from forming new blood vessels. If blood vessel growth is prevented, the cancer will lack the blood supply needed to grow. Some drugs can block blood vessel formation to cancer cells. Bevacizumab is a monoclonal antibody that blocks a growth factor needed by blood vessels. It is effective against kidney cancers and colon cancer. Other drugs, such as sorafenib and sunitinib, block the receptor for the blood vessel growth factor. These may be effective in kidney and liver cancers.

Still other drugs target the pathways cancer cells use to signal additional cells to form or grow.

Drugs Mentioned In This Article

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