The three main treatment approaches to cancer are surgery, radiation and chemotherapy. Surgery and radiation work best when the cancer is localized. Chemotherapy is used as a systemic approach. The drug is administered either by mouth or intravenous injection. It then enters the patient's system and affects tissues and organs on a more widespread basis.
How Cytotoxic Cancer Chemotherapy Works
In any cancer where there is no primary site of cancer growth, such as leukemia, chemotherapy is the treatment of choice because it can affect the entire body itself. Radiation is not an alternative because massive doses can prove lethal to the patient.
The basis for this treatment is that dividing or reproducing cells will be killed by cytotoxic drugs. These are drugs whose only function is to kill cells. They interrupt DNA and RNA, or genetic material and protein synthesis, which are instrumental in the growth of cells.
The genetic material of cells is DNA, which contains the cellular instructions for each particular cell to function. Cancer forces the DNA to be replicated at an abnormal rate for multiple cell growth. Since DNA controls its own growth, once it is destroyed the cell can no longer duplicate itself. The RNA is part of the genetic material that is derived from the DNA. It codes protein formation and carries messages from the DNA throughout the cell.
Once this DNA-RNA system is disrupted, cell function is skewed and the cell can't grow or reproduce and it dies. Cytoxic cancer chemotherapy slows the abnormal growth of cancer cells.
Protocols or Regimens for Chemotherapy Drugs
The dosage must be tailored to the type and stage of cancer as well as the patient's age and physical condition. The physical condition of the patient may include liver and kidney function and the presence of preexisting lung or heart disease.
A protocol is a combination of drugs that have been proven to be effective in treating a particular type of cancer. The dosage is calculated on the patient's mass rather than just the patient's body weight. This measurement is called the body surface area (BSA) and is usually expressed as square meters. The drug dosages are expressed as units per square meter. Dosage adjustments are made according to how the patient tolerates the protocol and the severity of the expected drug side effects or toxicities which may appear as hair loss, skin color changes, body sores, dehydration, weight loss, weakness, electrolyte imbalance, bone fractures and anorexia, to name a few.
Administration of the Drugs
The oral route is preferred but some cancer drugs may not be absorbed or may be destroyed by stomach acids and enzymes. Therefore the most common route is an internal administration which may be applied in various ways.
Intravenous Route
A vein is selected and punctured with a needle or a long plastic tube called an intravenous catheter. If the catheter must remain in the patient's body for a long period, it is usually placed in a large vein that enters the heart. The blood dilutes and spreads the chemotherapy drugs throughout the body quickly. These catheters can remain in the patient's body for years with proper care. The drug itself is given by injection into a port on the catheter.
Intra-arterial (IA) Injection
An artery is used instead of a vein. This method is preferred to infuse drugs in treating certain types of liver cancer and lung cancer as well as cancers of the head and neck.
Intrathecal (IT) Injection
Some drugs must be injected into the intrathecal space in the spinal cord so that they can more easily move into the central nervous system to treat cancers of the brain and major nerves. Many drugs can't penetrate the blood-brain barrier of the nervous system. The cells that compose this barrier restrict units that enter and leave the central nervous system as a means of protection.
Intracavity Injection
Sometimes chemotherapy drugs are injected directy into the body cavities to directly interact with tumors. Intravesical injection refers to the injection of drugs directly into the bladder to treat tumors on the inner lining of the bladder. Intraperitoneal injection is an infusion into the abdominal cavity. It is often used to treat ovarian cancers.
Additional List of Sources:Timothy F. Meiller, D.D.S., Ph.D. CancerPenn Foster. 2008. Scranton, PA
www.en.scientificcommons.org/timothy_f_meiller
www.biomedexperts.com/concept.bme/14585/neoplasms
www.mayoclinic.com/health/housecall/housecalls&insecure=1&unsecure
