Types of Chemotherapy Drugs
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Chemotherapy is one the many treatments for cancers found today. This treatment involves the use of drugs to treat tumors in the body. These drugs are categorized depending on their ability to kill tumor cells and can be administer in many ways. Doctors research and decide the protocol taken for the treatment of a patient. Chemotherapy has become very popular in the medical society and has become an effective way to treat cancer patients.
Chemotherapy is one of the treatments for tumors today. It was first discovered in 1940, but didn't really take off until the 1980s. (Prabhakar) Chemotherapy is known as a secondary treatment but can also be the only treatment given to a patient. (Treatment FAQ, Chemotherapy) It is usually used after a surgery or after radiotherapy treatments have been conducted on a patient to clean up any leftover tumor cells that could not be detected or removed during the surgery. (Brain Tumor: Treatment Cancer.Net, Chemotherapy)
Chemotherapy uses drugs to cure the fast growing cells which form a mass called a tumor as shown in figure 1. A tumor consist of fast dividing cells that have lost their ability stop dividing once they have been touched by their like cells. These drugs can be given in a mixture, or only one drug is supplied to a patient. (Brain Tumor: Treatment Cancer.Net, Chemotherapy) Each tumor is given a grade from 1 to 4. The higher the number the more serious the case of cancer is and more effect that tumor has on the patient. (Treatment FAQ) Just like normal cells, tumor cells are found in five different stages. G0 is the resting stage, G1 is known as the RNA stage, G2, is the construction of the mitotic apparatus and protein synthesis, stage S is the DNA synthesis, and lastly the M stage is the mitosis stage where the cell begins its division. (Chemotherapy Agents)
Some of the drugs in chemotherapy are cell cycle non-specific which means they can work during any stages of the cell cycle found in figure 2. Some are cell cycle specific, which means they work during a specific stage of the cell cycle. (Chemotherapy Agents) Either, cell cycle non-specific or cell cycle specific both do the same things which are to interfere with the cancerous cells ability to divide and grow.
The drugs used in chemotherapy interfere with the cancerous cells ability to rapidly divide which will eventually kill off the cells. This will prevent the tumor from growing and moving into different areas of the body. Chemotherapy drugs target fast dividing cells including normal cells as well as the cancer cells. That is why during chemotherapy treatment many people lose their hair or experience nausea and vomiting because the cells found in the digestive track and hair folics tend to divide at faster speeds. Even the blood cells and the cells found in a person's mouth are affected and will result in a low blood count and mouth sores. (Brain Tumor: Treatment Cancer.Net, Chemotherapy) These side effects are very minimal for the amount of good these drugs to for a patient.
Administered Chemotherapy Drugs
There are many ways chemotherapy drugs can be given to a patient. Depending on the types of drugs and severity of the situation a patient can either take these drugs orally (pills), with an IV, or the drugs can be administer with the use a disc-shaped polymer wafers (known as Gliadel wafers). In these wafers there will be the drug or drugs of choice that will help prevent the growth of the tumors, or reappearance of the tumor cells. The wafer is placed in the infected area and will gradually dissolve releasing the drugs into the patient. ("Brain Tumor: Treatment Cancer.Net) These drugs are given in cycles where there is an "on" period when the patient will be taken the drugs for 4 to 6 weeks. Then there is an "off" period where the patient will take a rest from the drug treatment. (Brain Tumor: Treatment Cancer.Net, Chemotherapy) The types of drugs and the duration of the treatment is all dependant on many variables.
Protocols for Chemotherapy Drugs
Chemotherapy has been closely studied, especially in the past 30 years. Research and information has been gathered about each drug and how they correspond to different tumors. (Prabhakar) This information has helped establish protocols that are now followed to distinguish the type and amount of drugs a patient should be taking.
When a doctor or sergeant prescribes a tumor patient drugs that they will need for treatment they look at many factors. One is the type a cancer and the stage it is in. Other factors such as weight, position of the tumor, age and other medical problems come into an effect when a doctor is prescribing their patient. (Chemotherapy Drugs) For example a doctor will not prescribe a 60 year old woman, with bad bowels, drugs that have a strong effect on the stomach. Another fact a sergeant or doctor will look at is the response rates. These rates establish the success rate and failure rate of drug(s) on a particular type of tumor. These rates distinguish how well the treatment went and how long the results were kept. (Chemotherapy Drugs) Doctors will of course choose the protocol with the best success rate as long as it does not interfere with any of the other factors.
Categories of Chemotherapy Drugs
Chemotherapy drugs have been classified into many different categories and subcategories based on their ability to destroy tumor cells. The first classification is known alkylating agents. These agents work by attacking the DNA by linking the guanine nucleobases (parts of DNA that is part of pairing) in DNA making the DNA unable to separate. (Wiki) These drugs are most effective during the resting stage of the cell cycle and can be given orally or intravenously. An example is Cyclophosphamide. (Chemotherapy Agents, Lee, Lyss) Nitrosourreas are very similar to alkylating drugs because they attack the DNA and making it unable to repair itself. These drugs are very useful for brain tumors because they are able to pass that blood-brain barrier. The blood brain barrier protects the brain from harmful chemicals and bacteria and becomes very difficult for chemotherapy drugs to pass through. Nitrosourreas have that special ability to pass through this barrier and treat brain tumors. These drugs can be given with an IV or can be found in pill form. An example of a Nitrosourreas is Carmustine. (Lee, Lyss, How Does Chemotherapy Work?) Anti-metabolites ask like purine (a substance used for the formation of DNA) which doesn't allow the real purine to become part of the DNA during the S phase of the cell cycle. This damages the DNA, and these drugs also affect the synthesis of the RNA as well. (Wiki) They are given in an IV or in pill form, an example being 6-mercaptopurine. (Lee, Lyss) Anti-tumor antibiotics are another category of drugs used for the treatment of tumors and work during many phase of the cell cycle. These drugs bind with the cells DNA and prevent the RNA to be synthesised which prevents the DNA from replicating itself. This drug is used for many treatments of cancers and is given as a pill or in IV form. An example is Doxorubicin. (Chemotherapy Agents, Lee, Lyss, How Does Chemotherapy Work?) These drugs affect the genetic information of a cell while, others affect the protein and receptors cells use.
Plant (vinca) Alkaloids are another category of chemotherapy drugs. These drugs stop cell division from occurring during metaphase. Metaphase is a stage in cell division where the chromosomes line up at the equatorial plane, this happens before the cell is ready to spilt up. The chromatin is attached to mitotic spindles which are formed through the use of the protein tubulin. To prevent the formation of the mitotic spindles, the plant alkaloids bind with the protein tubulin. The cell cannot divide if it does not have the mitotic spindles forming during cell division. These drugs are made from plants and can only be given intravenously. Examples are Vincristine and Vinblastine. (Chemotherapy Agents, Lee, Lyss, How Does Chemotherapy Work?) Steroid Hormones prevent the cell from binding to estrogen response element on the DNA by changing the shape of the receptors on the cell. These drugs are commonly used to treat breast cancer and are administered in pill form. Some examples of steroid hormones are Tamoxifen and Flutamide. (Lee, Lyss, How Does Chemotherapy Work?)The drugs affect the receptors of the cell while other are inhibitors for enzymes used by the tumor cells.
Anthracyclines are another category of chemotherapy drugs that affect the necessary enzymes need for the replication of the cell's DNA. They work during any part of the cell cycle, Bleomycin being one of them. (Chemotherapy Agents) Topoisomerase Inhibitors interfere with the duties of the toposiomerase enzyme. These enzymes are very important for controlling the manipulation of DNA structures that are needed for replication. Ironotecan is an example of Tropoisomerase Inhibitors. (Chemotherapy Agents) All these categories of drugs are different, but all lead to the same product, which is the destruction of the tumor cells.
Chemotherapy has proven to be a very effective treatment for tumors. There are many drugs out there today that have different way of affective tumors cells. Either by effective the DNA and RNA or effecting enzymes and proteins that are important for a cell division. Advancements in this treatment have made it a popular and an easy form of treatment for an everyday person. Researchers are currently looking for new and improved drugs that will help extinguish this growing problem in our world today. Though chemotherapy is not perfect, and cannot cure every patient, treatment is improving and the success rates are increasing.
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