Chemotherapy (Salem Health: Cancer)
- First-line or standard chemotherapy: Given to destroy cancerous cells before disease progression or recurrence; first-line chemotherapy has been determined, through research studies and clinical trials, to have the best probability of treating a certain type of cancer
- Second-line chemotherapy: Given to destroy cancerous cells when the disease has not responded to first-line chemotherapy or has recurred after first-line chemotherapy
- Adjuvant chemotherapy: Given to destroy cancerous cells that may remain after a known cancerous tumor has been surgically removed or after radiation therapy has been given
- Consolidation or intensification chemotherapy: Given once a remission is achieved, with the goal of sustaining a remission.
- Induction chemotherapy: Given to induce a remission
- Maintenance chemotherapy: Given in lower doses to help prolong a remission
- Palliative chemotherapy: Given to ease the symptoms of cancer and improve a patient’s quality of life
Cancers treated: All
Subclasses of this group: Alkylating agents, anthracyclines, antimetabolites, corticosteroid hormones, mitotic inhibitors, nitrosoureas, topoisomerase inhibitors; some chemotherapy drugs do not fit into these classifications, including dactinomycin (Cosmegen), hydroxyurea (Droxia), L-asparaginase (Elspar), procarbazine (Matulane), and thalidomide (Thalomid)...
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For Further Information (Salem Health: Cancer)
Chabner, Bruce A., and Dan L. Longo, eds. Cancer Chemotherapy and Biotherapy: Principles and Practice. Philadelphia: Lippincott Williams & Wilkins, 2006.
Fischer, David S., et al. The Cancer Chemotherapy Handbook. 6th ed. St. Louis: Mosby, 2003.
National Cancer Institute. Chemotherapy and You. NIH Publication No. 07-7156. Bethesda, Md.: National Institutes of Health, U.S. Department of Health and Human Services, 2007. Also available at http://www .cancer.gov.
Skeel, Roland T. Handbook of Cancer Chemotherapy. 7th ed. Philadelphia: Lippincott Williams & Wilkins, 2007.
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Indications and Procedures (Magill’s Medical Guide, Sixth Edition)
Chemotherapy refers to the concept of using chemicals in a therapeutic manner. Although chemotherapy is commonly associated with cancer, its concept and history actually encompass the use of medicinal approaches to treat many different types of human disease, such as bacterial and viral infections. In the early part of the twentieth century, Paul Ehrlich coined the term “chemotherapy” and defined it descriptively as a “chemical knife,” in effect a “magic bullet.” The work of Ehrlich established the principle that chemical substances could be used effectively in the treatment of human diseases. The success of chemotherapy is based on the simple principle of selective toxicity, which can be defined as the capacity of a drug to recognize and destroy an infectious agent or diseased cell without seriously harming the human body. The chemical knife envisioned by Ehrlich must be a selective one, or both the host and the pathogen will die.
In antibiotics, this targeting is achieved largely because of the vast structural differences between bacterial cells and human cells. For example, penicillin, discovered by British scientist Alexander Fleming as a product of the mold Penicillium notatum, targets a unique compound found only in bacterial cells. When antibiotics such as penicillin target the bacterial cell wall, the bacterial cell lyses, or falls apart and dies. Human cells lack cell walls and...
(The entire section is 1353 words.)
Uses and Complications (Magill’s Medical Guide, Sixth Edition)
Conventional chemotherapeutic drugs are divided into separate groups depending on their chemical properties and mechanism of cell destruction. Most clinical treatment protocols involve combination chemotherapy using several drugs with different cell targets. This approach is designed to employ multifaceted targeting as a way of achieving maximum cell destruction in a single round of treatment and, in conjunction with high-dose or “dose dense” approaches, is thought to produce maximum effects with the least likelihood of triggering the new growth of drug-resistant tumors. All treatment protocols are designed and implemented only after rigorous preclinical trials are conducted to ascertain their effectiveness against a particular type of cancer. The important classes of standard anticancer drugs are summarized below.
Alkylating agents block the synthesis of DNA by chemically modifying its structure. The nitrogen mustards were the first chemical drugs to be used in the treatment of cancer. Today, cyclophosphamide is commonly used in combined treatment approaches in patients with leukemia and lymphoma. The nitrosoureas, a second group of alkylating agents, interact with DNA by forming chemical cross-links that result in DNA strand breakage. They can enter the cerebrospinal fluid and are therefore used to treat brain tumors. Examples include carmustine and busulfan.
The antimetabolites share structural...
(The entire section is 948 words.)
Perspective and Prospects (Magill’s Medical Guide, Sixth Edition)
The idea of chemotherapy is not a new one; it dates back to the days of antiquity. Approximately 2,500 years ago, ancient Egyptian writings about cancer first appeared, along with treatment recommendations such as the use of barley, castor beans, and pig ears to treat cancers of the stomach and uterus. After the ancient Egyptians, among the earliest recorded chemotherapies involved the use of mercury to treat outbreaks of syphilis in Europe in the late fifteenth century. In North America, early American Indians chewed the bark of the cinchona tree to ward off malaria, and by 1630 it was recognized by Europeans that this medicinal bark contained an antimalarial substance called quinine, which eventually became a widely used treatment for malarial infections.
One of the most significant advances in the development of modern chemotherapy was the pioneering work of Paul Ehrlich in the early part of the twentieth century. His efforts to find a “magic bullet” to selectively destroy infectious disease agents culminated in the isolation of a synthetic arsenic compound called salvarsan, which was used in the treatment of syphilis.
In 1929, Alexander Fleming made the monumental discovery that penicillin, an extract from a common mold, could kill infectious bacterial pathogens. He made this astonishing finding upon examining a set of moldy, contaminated culture dishes that he was preparing to discard when he noticed...
(The entire section is 937 words.)
For Further Information: (Magill’s Medical Guide, Sixth Edition)
Bruning, Nancy. Coping with Chemotherapy. Rev. ed. New York: Ballantine Books, 1993. Takes a practical approach to dealing with the difficulties and side effects of cancer chemotherapy.
Brunton, Laurence L., et al., eds. Goodman and Gilman’s “The Pharmacological Basis of Therapeutics.” 11th ed. New York: McGraw-Hill, 2006. This reference book provides a detailed explanation of the principles of cancer drug treatments. Offers comprehensive coverage at a somewhat advanced level.
Clarke, Michael, et al. “Stem Cells: The Real Culprit in Cancer?” Scientific American 295, no. 1 (July, 2006): 52-59. Discusses the possible significance of cancer stem cells and their potential as a target for chemotherapy.
Fischer, David S. The Cancer Chemotherapy Handbook. 6th ed. St. Louis, Mo.: Mosby, 2003. Presents a broad-based approach to cancer chemotherapy, nutritional supplements, and basic treatment approaches.
Quillin, Patrick. Beating Cancer with Nutrition. Rev. ed. Tulsa, Okla.: Nutrition Times Press, 2005. Describes nutritional approaches as a way of enhancing cancer therapies and their effectiveness.
(The entire section is 152 words.)
Chemotherapy (Encyclopedia of Cancer)
Chemotherapy is the systemic (whole body) treatment of cancer with anticancer drugs.
The main purpose of chemotherapy is to kill cancer cells. It can be used as the primary form of treatment or as a supplement to other treatments. Chemotherapy is often used to treat patients with cancer that has spread from the place in the body where it started (metastasized), but it may also be used the keep cancer from coming back (adjuvant therapy). Chemotherapy destroys cancer cells anywhere in the body. It even kills cells that have broken off from the main tumor and traveled through the blood or lymph systems to other parts of the body.
Chemotherapy can cure some types of cancer. In some cases, it is used to slow the growth of cancer cells or to keep the cancer from spreading to other parts of the body. When a cancer has been removed by surgery, chemotherapy may be used to keep the cancer from coming back (adjuvant therapy). It is also helpful in reducing the tumor size prior to surgery (primary [neoadjuvant] chemotherapy). Chemotherapy can ease the symptoms of cancer (palliate), helping some patients have a better quality of life.
(The entire section is 5909 words.)
Chemotherapy (Encyclopedia of Medicine)
Chemotherapy is treatment of cancer with anticancer drugs.
The main purpose of chemotherapy is to kill cancer cells. It is usually used to treat patients with cancer that has spread from the place in the body where it started (metastasized). Chemotherapy destroys cancer cells anywhere in the body. It even kills cells that have broken off from the main tumor and traveled through the blood or lymph systems to other parts of the body.
Chemotherapy can cure some types of cancer. In some cases, it is used to slow the growth of cancer cells or to keep the cancer from spreading to other parts of the body. When a cancer has been removed by surgery, chemotherapy may be used to keep the cancer from coming back (adjuvant therapy). Chemotherapy also can ease the symptoms of cancer, helping some patients to have a better quality of life.
There are many different types of chemotherapy drugs. Oncologists, doctors who specialize in treating cancer, determine which drugs are best suited for each patient. This decision is based on the type of cancer, the patient's age and health, and other drugs the patient is taking. Some patients should not be treated with certain chemotherapy drugs. Age and other conditions may affect the drugs...
(The entire section is 2300 words.)
Chemotherapy (Encyclopedia of Children's Health)
Chemotherapy, sometimes referred to as "chemo," is the treatment of cancer with anticancer drugs.
The main purpose of chemotherapy is to kill cancer cells. It usually is used to treat patients with cancer that has spread from the place in the body where it originated (metastasized). Chemotherapy destroys cancer cells anywhere in the body. It even kills cells that have broken off from the main tumor and traveled through the blood or lymph systems to other parts of the body.
Chemotherapy can cure some types of cancer. In some cases, it is used to slow the growth of cancer cells or to keep the cancer from spreading to other parts of the body. Chemotherapy may be given before surgery or radiation therapy to shrink the tumor (neoadjuvant therapy). When a cancer has been removed by surgery or treated with radiation therapy, chemotherapy may be used to keep the cancer from coming back (adjuvant therapy).
Once a remission is achieved, consolidation chemotherapy, also called intensification chemotherapy, is given to sustain a remission. Maintenance chemotherapy is chemotherapy given in lower doses as a treatment to prolong a remission in certain types of cancer. Chemotherapy also can ease the...
(The entire section is 4645 words.)
Chemotherapy (Encyclopedia of Nursing & Allied Health)
Chemotherapy is the treatment of cancer with anti- cancer drugs.
The purpose of chemotherapy is to kill cancer cells. Not only is it often used to treat patients with cancer that has metastasized (spread) from the site in the body where it originated, today chemotherapy can be used to prevent metastasis as well. Chemotherapy destroys cancer cells throughout the body, killing cells that have broken off from the main tumor and traveled through the blood or lymph systems to other parts of the body.
Chemotherapy can cure some types of cancer. In some cases, it is used to slow the growth of cancer cells or to keep the cancer from spreading to other parts of the body. When a cancer has been removed by surgery, chemotherapy may be used to keep the cancer from recurring; this is known as adjuvant therapy. Chemotherapy also can ease the symptoms of cancer, helping some patients to have a better quality of life.
There are many different types of chemotherapy drugs. Oncologists (specialists in cancer) determine which drugs are best suited for each patient. This decision is based on the type of cancer, the patient's age, health, and preferences, as well as other drugs the patient is taking. Some patients may not tolerate certain chemotherapy drugs if they have other illnesses such as heart disease, kidney disease, or diabetes.
Chemotherapy, whether administered in the hospital, clinic, or at home, is prepared by the pharmacist. The pharmacy and pharmacy assistants provide and reinforce patient education about common as well as infrequent side effects of chemotherapy. When administered in the hospital, clinic, physician's office, or other treatment setting, it is usually administered by a specially trained nurse, mid-level practitioner (physician assistant of nurse practitioner), or physician.
More than 50 chemotherapy drugs are currently available to treat cancer, and many more are being tested for their ability to destroy cancer cells. Most chemotherapy drugs interfere with the ability of cells to grow or multiply. Although these drugs affect all cells in the body, most useful treatments are more effective against rapidly growing cancer cells. Since chemotherapy affects rapidly growing cells, it often affects cells that normally grow rapidly such as cells in the bone marrow, stomach intestines, and hair follicles. This is why some of the most common side effects of chemotherapy are bone marrow suppression, nausea, vomiting, and hair loss.
Types of chemotherapy drugs
Chemotherapy drugs are classified based on their mechanisms of action (how they work). The main types of chemotherapy drugs are:
- Alkylating drugs kill cancer cells by directly attacking DNA, the genetic material of the genes. Cyclophosphamide is an example of an alkylating drug.
- Antimetabolites interfere with the production of DNA thereby preventing cells from growing and multiplying. An example of an antimetabolite is 5-fluorouracil (5-FU).
- Antitumor antibiotics are made from natural substances such as fungi in the soil. They interfere with important cell functions, including production of DNA and cell proteins. Doxorubicin and bleomycin belong to this group of chemotherapy drugs.
- Plant alkaloids prevent cells from dividing normally. Vinblastine and vincristine are plant alkaloids obtained from the periwinkle plant.
- Steroid hormones slow the growth of some cancers that depend on hormones. For example, tamoxifen is used to treat breast cancers that depend on the hormone estrogen for growth.
The oncologist decides which chemotherapy drug or combination of drugs will work best for each patient. The use of two or more drugs together often works better than a single drug alone. This is called combination chemotherapy. Scientific studies and clinical research trials of different drug combinations help determine which combinations are most effective for each type of cancer.
How chemotherapy is administered
Chemotherapy is administered in different ways, depending on the drugs to be given and the type of cancer. The prescribed dose depends on several factors, one of which is the patient's body weight.
Chemotherapy may be administered by one or more of the following methods:
- intramuscular (IM) or subcutaneous injection
- through a catheter or port
Oral chemotherapy, given by mouth, may be in the form of a pill, capsule, or liquid. This is the easiest method of administration and can usually be done at home.
Intravenous (IV) chemotherapy is injected into a vein. A small needle is inserted into a vein on the hand or lower arm. The needle is usually attached to a small tube called a catheter, which delivers the drug to the needle from an IV bag or bottle.
Intramuscular (IM) chemotherapy is injected into a muscle. Chemotherapy given by intramuscular injection is absorbed into the blood more slowly than IV chemotherapy. Because of this, the effects of IM chemotherapy may last longer than chemotherapy given intravenously. Chemotherapy may also be injected subcutaneously (under the skin). Injection of chemotherapy directly into the cancer is called intralesional injection.
Chemotherapy may also be given by a catheter or port permanently inserted into a central vein or body cavity. A port is a small reservoir or container that is placed in a vein or under the skin in the area where the drug will be administered. These methods eliminate the need for repeated injections and may allow patients to spend less time in the hospital while receiving chemotherapy. A common location for a permanent catheter is the external jugular vein in the neck. Intraperitoneal (IP) chemotherapy is administered into the abdominal cavity through a catheter or port. Chemotherapy administered by catheter or port into the spinal fluid surrounding the brain or spine is called intrathecal (IT) administration. Catheters and ports may also be placed in the chest cavity, bladder, or pelvis, depending on the location of the cancer to be treated.
Topical chemotherapy is given as a cream or ointment applied directly to the cancer. It may be used to treat certain types of skin cancer.
Treatment location and schedule
Patients may take chemotherapy at home, in the physician's office, or as an inpatient or outpatient at the hospital. Many patients stay in the hospital when first beginning chemotherapy, so they can be observed and monitored for any side effects.
The frequency and duration of chemotherapy given depends on the type of cancer, the patient response to the drugs, patients' overall health and ability to tolerate the drugs, and on the types of drugs used. Chemotherapy administration may take only a few minutes or may last as long as several hours. Chemotherapy may be given daily, weekly, or monthly. A rest period may follow a course of treatment before the next course begins. In combination chemotherapy, more than one drug may be given at the same time, or they may be given alternately, one following the other.
A number of medical tests are performed before chemotherapy is started. The oncologist will determine the extent to which the cancer has spread from the results of x rays and other imaging tests and from biopsies. Radiologic technologists and technicians perform imaging studies. Analysis of the biopsy will be performed by a pathologist, assisted by laboratory technicians.
Blood tests, drawn by laboratory technicians or nurses, provide important information about the function of the blood cells and levels of chemicals in the blood. A complete blood count (CBC) is commonly performed before and on a regular basis during treatment. The CBC shows the numbers of white blood cells, red blood cells, and platelets in the blood. Because chemotherapy affects the bone marrow, where blood cells are made, levels of these cells often drop during chemotherapy. The white blood cells and platelets are most likely to be affected by chemotherapy. A drop in the white blood cell count means that the immune system may not function prop- erly and the patient may become prone to infection. Low levels of platelets may cause a patient to bleed from minimal trauma or even spontaneously with no trauma. A low red blood cell count can lead to anemia (deficiency of red blood cells) and fatigue.
Sometimes, patients taking chemotherapy drugs known to cause nausea are given antiemetics before chemotherapy is administered to lessen feelings of nausea. Two anti-nausea medications that may be used are Kytril and Zofran.
Patients may also be advised to prepare for chemotherapy and reduce nausea by eating and drinking normally until about two hours before a chemotherapy session. They should eat high carbohydrate, low-fat foods and avoid spicy foods.
Patient education about how to control side effects after chemotherapy includes:
- Encouraging patients to adhere to instructions given by their health care team.
- Reinforcing correct use of all prescribed medications.
- Advising patients to eat small amounts of bland foods and drink lots of fluids.
- Instructing patients to get plenty of rest.
Some patients find that breathing fresh air or mild exercise, such as walking, helps to relieve the stress and side effects associated with chemotherapy.
Chemotherapy drugs are toxic to normal cells as well as cancer cells. Doses that will destroy cancer cells will likely cause damage to some normal cells. Physicians adjust (titrate) doses to do the least amount of harm possible to normal cells. Some patients feel few or no side effects, and others may experience more serious side effects. In some cases, a dose adjustment is all that is needed to reduce or stop a side effect.
Some chemotherapy drugs have more side effects than others. The most common side effects include:
- nausea and vomitingloss of appetite
- hair loss (alopecia)
- anemia and fatigue
- easy bleeding or bruising
- sores in the mouth and throat
- neuropathy and other damage to the nervous system
- kidney damage
Nausea and vomiting are common, but can usually be controlled by taking antinausea drugs, drinking enough fluids, and avoiding spicy foods. Loss of appetite may be due to nausea or the stress of undergoing cancer treatment. Also, although some chemotherapy drugs cause alopecia, it is almost always temporary and reversible.
Low blood cell counts caused by the effect of chemotherapy on the bone marrow can lead to anemia, infections, and easy bleeding and bruising. Patients with anemia have too few red blood cells to deliver oxygen and nutrients to the body's tissues. Anemic patients feel tired and weak. If red blood cell levels fall too low, a blood transfusion may be given.
Patients receiving chemotherapy are more likely to get infections because white blood cells are reduced. It is important to take measures to avoid infections. When the white blood cell count drops too low, the physician may prescribe medications called colony-stimulating factors that help white blood cells grow. Neupogen and Leukine are two colony stimulants used as treatments to help fight infection.
Platelets are blood particles that make the blood clot. When patients do not have enough platelets, they may bleed or bruise easily, even from small injuries. Patients with low blood platelets should be advised to take precautions to avoid injuries. Medicines such as aspirin and other pain relievers can impair platelet function and slow the clotting process.
Chemotherapy can cause irritation and dryness in the mouth and throat. Painful sores may form that can bleed and become infected. Patients should be advised about actions they might take to prevent or reduce mouth irritation. Precautions to avoid this side effect include dental care before chemotherapy begins, brushing the teeth and gums regularly with a soft brush, and avoiding mouth- washes that contain salt or alcohol.
The primary goal of chemotherapy is to cure cancer. Some cancers, such as Hodgkin's disease and acute lymphocytic
leukemia, may be cured by chemotherapy. Used as adjuvant therapy, in combination with surgery, it may prevent a cancer from spreading to other parts of the body. Some widespread, fast-growing cancers are more difficult to treat. In these cases, chemotherapy may slow the growth of the cancer cells.
Physicians determine the extent to which chemotherapy is effective by closely monitoring the results of medical tests. Physical examination, blood tests, and imaging studies are used to monitor and assess the effects of treatment on the cancer.
The outcomes of chemotherapy include:
- Complete remission or complete response. The cancer completely disappears. The course of chemotherapy is completed, and the patient is tested regularly for a recurrence.
- Partial remission or partial response. The cancer shrinks in size but does not disappear. The same course of chemotherapy may be continued, or a different combination of drugs may be tried.
- Stabilization. The cancer does not grow or shrink. Other therapy options may be explored. A tumor may remain stabilized for many years.
- Progression. The cancer continues to grow. Other therapy options may be explored.
- A new type of malignancy may develop, and this secondary cancer may require additional chemotherapy or other treatment.
Health care team roles
Patients with cancer are usually cared for by a multidisciplinary team of health professionals. The patient's family physician or primary care physician collaborates with other specialists, such as surgeons and oncologists. Radiologic technicians perform imaging studies, and nurses and laboratory technicians may obtain samples of blood, urine, and other laboratory tests.
Before and after chemotherapy, nurses explain the goals and effects of drug treatment and help to prepare patients and families. Depending on the treatment plan, cancer patients may also benefit from rehabilitation therapy with physical therapists, nutritional counseling from dieticians, and counseling from social workers or other mental health professionals.
Adjuvant therapyreatment given after surgery or radiation therapy to prevent the cancer from coming back.
Alkaloid type of chemical commonly found in plants and often having medicinal properties.
Alykylating drug drug that kills cells by direct- ly damaging DNA.
Antiemetic medicine that helps control nausea; also called an anti-nausea drug.
Antimetabolite drug that interferes with a cell's growth or ability to multiply.
Plateletslood cells that function in blood clotting.
Dollinger, Malin, Ernest H. Rosenbaum, and Greg Cable. Everyone's Guide to Cancer Therapy. Kansas City, MO: Andrews McMeel Publishing, 1998.
American Cancer Society. 1599 Clifton Road, N.E., Atlanta, GA 30329. (800) ACS-2345.
Cancer Information Service of the National Cancer Institute. (800) 4-CANCER.
"Chemotherapy and You: A Guide to Self-Help During Treatment." National Cancer Institute. National Institutes of Health. <<a href="http://www.cancernet.nci.nih.gov/chemotherapy/chemoint.html">http://www.cancernet.nci.nih.gov/chemotherapy/chemoint.html>.
"Introduction to Chemotherapy." OncoLink, University of Pennsylvania Cancer Center. 1998. <<a href="http://www.oncolink.upenn.edu/specialty/chemo/general/chemo_intro.htm.l">http://www.oncolink.upenn.edu/specialty/chemo/general/chemo... >.
Barbara Wexler, M.P.H.
Chemotherapy (World of Microbiology and Immunology)
Chemotherapy is the treatment of a disease or condition with chemicals that have a specific effect on its cause, such as a microorganism or cancer cell. The first modern therapeutic chemical was derived from a synthetic dye. The sulfonamide drugs developed in the 1930s, penicillin and other antibiotics of the 1940s, hormones in the 1950s, and more recent drugs that interfere with cancer cell metabolism and reproduction have all been part of the chemotherapeutic arsenal.
The first drug to treat widespread bacteria was developed in the mid-1930s by the German physician-chemist Gerhard Domagk. In 1932, he discovered that a dye named prontosil killed streptococcus bacteria, and it was quickly used medically on both streptococcus and staphylococcus. One of the first patients cured with it was Domagk's own daughter. In 1936, the Swiss biochemist Daniele Bovet, working at the Pasteur Institute in Paris, showed that only a part of prontosil was active, a sulfonamide radical long known to chemists. Because it was much less expensive to produce, sulfonamide soon became the basis for several widely used "sulfa drugs" that revolutionized the treatment of formerly fatal diseases. These included pneumonia, meningitis, and puerperal ("childbed") fever. For his work, Domagk received the 1939 Nobel Prize in physiology or medicine. Though largely replaced by antibiotics, sulfa drugs are still commonly used against urinary tract infections, Hanson disease (leprosy), malaria, and for burn treatment.
At the same time, the next breakthrough in chemotherapy, penicillin, was in the wings. In 1928, the British bacteriologist Alexander Fleming noticed that a mold on an uncovered laboratory dish of staphylococcus destroyed the bacteria. He identified the mold as Penicillium notatum, which was related to ordinary bread mold. Fleming named the mold's active substance penicillin, but was unable to isolate it.
In 1939, the American microbiologist René Jules Dubos (1901982) isolated from a soil microorganism an antibacterial substance that he named tyrothricin. This led to wide interest in penicillin, which was isolated in 1941 by two biochemists at Oxford University, Howard Florey and Ernst Chain.
The term antibiotic was coined by American microbiologist Selman Abraham Waksman, who discovered the first antibiotic that was effective on gram-negative bacteria. Isolating it from a Streptomyces fungus that he had studied for decades, Waksman named his antibiotic streptomycin. Though streptomycin occasionally resulted in unwanted side effects, it paved the way for the discovery of other antibiotics. The first of the tetracyclines was discovered in 1948 by the American botanist Benjamin Minge Duggar. Working with Streptomyces aureofaciens at the Lederle division of the American Cyanamid Co., Duggar discovered chlortetracycline (Aureomycin).
The first effective chemotherapeutic agent against viruses was acyclovir, produced in the early 1950s by the American biochemists George Hitchings and Gertrude Belle Elion for the treatment of herpes. Today's antiviral drugs are being used to inhibit the reproductive cycle of both DNA and RNA viruses. For example, two drugs are used against the influenza A virus, Amantadine and Rimantadine, and the AIDS treatment drug AZT inhibits the reproduction of the human immunodeficiency virus (HIV).
Cancer treatment scientists began trying various chemical compounds for use as cancer treatments as early as the mid-nineteenth century. But the first effective treatments were the sex hormones, first used in 1945, estrogens for prostate cancer and both estrogens and androgens to treat breast cancer. In 1946, the American scientist Cornelius Rhoads developed the first drug especially for cancer treatment. It was an alkylating compound, derived from the chemical warfare agent nitrogen mustard, which binds with chemical groups in the cell's DNA, keeping it from reproducing. Alkylating compounds are still important in cancer treatment.
In the next twenty years, scientists developed a series of useful antineoplastic (anti-cancer) drugs, and, in 1954, the forerunner of the National Cancer Institute was established in Bethesda, MD. Leading the research efforts were the so-called "4-H Club" of cancer chemotherapy: the Americans Charles Huggins (1901997), who worked with hormones; George Hitchings (1905998), purines and pyrimidines to interfere with cell metabolism; Charles Heidelberger, fluorinated compounds; and British scientist Alexander Haddow (1907976), who worked with various substances. The first widely used drug was 6-Mercaptopurine, synthesized by Elion and Hitchings in 1952.
Chemotherapy is used alone, in combination, and along with radiation and/or surgery, with varying success rates, depending on the type of cancer and whether it is localized or has spread to other parts of the body. They are also used after treatment to keep the cancer from recurring (adjuvant therapy). Since many of the drugs have severe side effects, their value must always be weighed against the serious short-and long-term effects, particularly in children, whose bodies are still growing and developing.
In addition to the male and female sex hormones androgen, estrogen, and progestins, scientists also use the hormone somatostatin, which inhibits production of growth hormone and growth factors. They also use substances that inhibit the action of the body's own hormones. An example is Tamoxifen, used against breast cancer. Normally the body's own estrogen causes growth of breast tissues, including the cancer. The drug binds to cell receptors instead, causing reduction of tissue and cancer cell size.
Forms of the B-vitamin folic acid were found to be useful in disrupting cancer cell metabolism by the American scientist Sidney Farber (1903973) in 1948. Today they are used on leukemia, breast cancer, and other cancers.
Plant alkaloids have long been used as medicines, such as colchicine from the autumn crocus. Cancer therapy drugs include vincristine and vinblastine, derived from the pink periwinkle by American Irving S. Johnson (1925). They prevent mitosis (division) in cancer cells. VP-16 and VM-16 are derived from the roots and rhizomes of the may apple or mandrake plant, and are used to treat various cancers. Taxol, which is derived from the bark of several species of yew trees, was discovered in 1978, and is used for treatment of ovarian and breast cancer.
Another class of naturally occurring substances are anthracyclines, which scientists consider to be extremely useful against breast, lung, thyroid, stomach, and other cancers.
Certain antibiotics are also effective against cancer cells by binding to DNA and inhibiting RNA and protein synthesis. Actinomycin D, derived from Streptomyces, was discovered by Selman Waksman and first used in 1965 by American researcher Seymour Farber. It is now used against cancer of female reproductive organs, brain tumors, and other cancers.
A form of the metal platinum called cisplatin stops cancer cells' division and disrupts their growth pattern. Newer treatments that are biological or based on proteins or genetic material and can target specific cells are also being developed. Monoclonal antibodies are genetically engineered copies of proteins used by the immune system to fight disease. Rituximab was the first moncoclonal antibody approved for use in cancer, and more are under development. Interferons are proteins released by cells when invaded by a virus. Interferons serve to alert the body's immune system of an impending attack, thus causing the production of other proteins that fight off disease. Interferons are being studied for treating a number of cancers, including a form of skin cancer called multiple myeloma. A third group of drugs are called anti-sense drugs, which affect specific genes within cells. Made of genetic material that binds with and neutralizes messenger-RNA, anti-sense drugs halt the production of proteins within the cancer cell.
Genetically engineered cancer vaccines are also being tested against several virus-related cancers, including liver, cervix, nose and throat, kidney, lung, and prostate cancers. The primary goal of genetically engineered vaccines is to trigger the body's immune system to produce more cells that will react to and kill cancer cells. One approach involves isolating white blood cells that will kill cancer and then to find certain antigens, or proteins, that can be taken from these cells and injected into the patient to spur on the immune system. A "vaccine gene gun" has also been developed to inject DNA directly into the tumor cell. An RNA cancer vaccine is also being tested. Unlike most vaccines, which have been primarily tailored for specific patients and cancers, the RNA cancer vaccine is designed to treat a broad number of cancers in many patients.
As research into cancer treatment continues, new cancer-fighting drugs will continue to become part of the medical armamentarium. Many of these drugs will come from the burgeoning biotechnology industry and promise to have fewer side effects than traditional chemotherapy and radiation.
See also Antibiotic resistance, tests for; Antiviral drugs; Bacteria and bacterial infection; Blood borne infections; Cell cycle and cell division; Germ theory of disease; History of microbiology; History of public health; Immunization