Chemotherapy is the use of drugs or chemicals, often in combinations, to kill or damage cancer cells in the body. This is why chemotherapy drugs are often called anti-cancer agents.
Today’s treatments for leukemia, lymphoma and myeloma include chemotherapy and radiation therapy, sometimes in combination. Very high dose chemotherapy followed by stem cell transplantation may also be used in treatment.
The progress in treatment and survival for patients with blood cancers is largely due to the development of chemotherapy drugs over the past 40 years. The number of chemotherapy agents available has soared since their first usage in the 1940s. Today, numerous drugs are available and may be used, either alone or in combination with one another, to achieve maximum cancer cell-fighting ability. Chemotherapy used to treat leukemia, lymphoma and myeloma may be accompanied by undesirable side effects.
It all begins with normal cells versus cancer cells. Normal, healthy cells divide and grow in a controlled fashion. As they divide, a replica is produced. Cancer cells, on the other hand, grow uncontrollably and rapidly. There is no pattern at all. When in contact with a normal cell, the cancer cell takes over and copies itself many times over. In this way, the body becomes overburdened with cancer cells. The goal of chemotherapy is either to kill cancer cells to the point that there is no longer any sign of illness (called remission), or to damage or kill cancer cells to the point that the progress of the disease is slowed. Chemotherapy can produce long-term remission or outright cure for many persons, depending on the specific type and extent of the cancer.
All chemotherapy drugs interfere with cancer cells’ ability to grow or multiply. Different groups of drugs act in different ways on cells’ ability to grow or multiply. Identification of the type of disease cell is important because certain chemotherapy drugs are given only for certain disease cell types.
More types of chemotherapy drugs, which act to kill cancer cells by different methods, continue to emerge with more progress in research. Many chemotherapy drugs act against cancer cells by interacting with the DNA or RNA, or the genetic makeup, of the cancer cell. This interaction changes the DNA in such a way that the cancer cell is killed or is prevented from growing or dividing and producing more cancer cells. Four of the chemotherapy drug types that act directly to impair the DNA in cancer cells are the DNA-damaging agents; antitumor antibiotics; antimetabolites; and DNA-repair enzyme inhibitors. DNA-damaging agents, such as chlorambucil, cyclophosphamide or melphalan are referred to collectively as alkylating agents. These DNA-damaging agents damage the DNA so severely that the cancer cell is killed. Other DNA-damaging agents, such as carboplatinum, attach to the DNA and prevent the cancer cell from growing.
Antitumor antibiotics, such as daunorubicin, doxorubicin, idarubicin, and mitoxantrone, insert themselves into the DNA of the cancer cell, prevent the DNA from functioning normally and often kill the cancer cell.
Antimetabolites, such as methotrexate, fludarabine, and cytarabine, are drugs that mimic substances that the cancer cell needs to build DNA and RNA. When the cancer cell uses the antimetabolite instead of the natural substances, it cannot produce normal DNA or RNA, and the cell dies.
DNA-repair enzyme inhibitors, such as etoposide or topotecan, attack the cancer cell proteins that normally repair any damage to the cell DNA. Repair of DNA damage is a normal and vital process in the cell. Without this repair process, the cancer cell is much more susceptible to damage and is prevented from growing. High doses of hormones, such as prednisone and dexamethasone, can kill lymphoma or lymphocytic leukemia cells.
Another type of chemotherapy drugs, such as vincristine or vinblastine, damage cancer cells by blocking a process called mitosis, preventing the cancer cells from dividing and multiplying.
Finally, a new group of chemotherapy agents consists of antibodies that are made specifically to attach to cancer cells. Once these antibodies attach to the cancer cells, they interfere with the cell’s function and kill the cell. In addition, some antibodies are linked to a toxin or radioactive substance. When the antibody attaches to the cancer cell, the antibody and the toxin or radioactive substance each work to kill the cell.
Chemotherapy drugs are often given in combination with each other, and can be given in different ways. The four most common methods are: intravenous, oral, intramuscular and intrathecal. The method is based on the actual disease diagnosed and the agent’s effectiveness.
The intravenous route, or IV, is a very common way of giving medicine directly into a vein. A small plastic needle is inserted into one of the veins in the lower arm. There is some discomfort during insertion because a needle stick is required to get into the vein. After that, administration of the medication is almost painless. Chemotherapy flows from a plastic bag, through tubing into the bloodstream. Sometimes a syringe is used to push the chemotherapy through the tubing. This method is especially useful for delivering drugs that might damage tissues if given by mouth or by injection.
The oral method takes the form of a pill, capsule or liquid taken by mouth. This is the easiest and most convenient method since it can be done at home. The term intramuscular means that the drug is injected into the muscle. There is a slight pinch as the needle is placed into the muscle of the arm, thigh or buttocks. However, the procedure lasts only a few seconds. Some chemotherapy drugs may be given by injection into the tissue under the skin, rather than into the muscle. This is referred to as a subcutaneous injection.
Certain types of leukemia and lymphoma have a tendency to spread to the nervous system. To prevent or to treat this, doctors may perform a spinal tap and inject a chemotherapy drug into the spinal fluid to destroy any cancer cells. This is known as an intrathecal method of administration. If many treatments are needed, doctors may place a permanent device, called an Omaya reservoir, under the scalp. Once the Omaya reservoir is inserted, chemotherapy treatments can be given through this device and the patient will no longer need spinal taps. The patient can go home with the Omaya reservoir in place.
The goal of chemotherapy is to destroy cancer cells. Although most of the effect of chemotherapy drugs does amount to the injury or death of cancer cells, the drugs also affect normal cells, causing certain side effects. The side effects of different chemotherapy drugs are known from previously conducted clinical trials, or research studies. These expected side effects are different depending on which drugs are being used, how the drugs are being given (oral, IV, injection), and for how long the drug is being given.
The most common side effects of chemotherapy drugs affect three main types of tissue in the body: the lining of the gastrointestinal tract, the skin and scalp (hair follicles), and the bone marrow. Each of these areas depends on the rapid growth of new cells to perform their normal functions in the body.
· Burning sensation or pain in the mouth
· Diarrhea and constipation
· Nausea and vomiting
Skin and hair:
· Skin rashes
· Hair loss
· Cell count changes
Sometimes having to make choices about chemotherapy and other treatment options can cause a great deal of anxiety. Often, if patients with cancer ask their doctor about the medical questions they have, this provides some sense of relief in making these choices. In addition, the patient’s nurses, social workers, and other health professionals understand the complexity of the emotions and special ongoing needs of those undergoing chemotherapy. They are available to spend time with the patient, answer questions, lend emotional support and provide referrals to other useful resources.