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Chemotherapy and Other Systemic Cancer Treatments

By

Robert Peter Gale

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

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

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.

Hormonal Therapy for Cancer

Hormones are proteins produced by endocrine glands Endocrine Glands The endocrine system consists of a group of glands and organs that regulate and control various body functions by producing and secreting hormones. Hormones are chemical substances that affect... read more 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 begins in a small area of the prostate gland, an organ found only in males. The risk of prostate cancer increases as men age. Symptoms, such as difficulty urinating, a need to... read more 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 The pituitary is a pea-sized gland that is housed within a bony structure (sella turcica) at the base of the brain. The sella turcica protects the pituitary but allows very little room for expansion... read more 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 occurs when cells in the breast become abnormal and divide uncontrollably. Breast cancer usually starts in the glands that produce milk (lobules) or the tubes (ducts) that carry... read more 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

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) Chronic myeloid leukemia is a slowly progressing disease in which cells that normally would develop into the types of white blood cells called neutrophils, basophils, eosinophils, and monocytes... read more 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 Although gene therapy is defined as any treatment that changes gene function, it is often thought of as the insertion of normal genes into the cells of a person who lacks such normal genes because... read more ). 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 Cancer drugs are most effective when given in combination. The rationale for combination therapy is to use drugs that work by different mechanisms, thereby decreasing the likelihood that resistant... read more . 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.

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