Understand Childhood Cancers and Blood Disorders
Chemotherapy is the term generally used for medications that kill cancer cells. Chemotherapy is one of the treatments for cancer. Other cancer treatments include surgery, radiotherapy, immunotherapy (also known as biological therapy), hormonal therapy, and others.
Normal cells go through a "life cycle" - they are made (born), they grow and perform specific functions within a tissue or organ. They can repair damage to their DNA, and ultimately die in a controlled manner. By contrast, cancer cells replicate in an uncontrolled fashion, do not perform any specific function well, are unable to repair damage to their DNA, and do not die in a controlled and timely manner.
Chemotherapy works against rapidly dividing cancer cells by stopping them from growing or multiplying. Different drugs work against the cancer cells in different ways. For example, some drugs prevent a cancer cell from duplicating its DNA, thereby preventing it from creating another copy of itself. Other medications interfere with the actual process of cell division thereby again preventing the cancer cell from producing another identical copy of itself. Another class of chemotherapy medications interferes with the ability of the cell to get the necessary proteins it needs, thus literally "starving" the cell to death. Some drugs work against the cancer cells in all phases of their life cycle, while others kill those abnormal cells only during specific stages of those cells' lives.
From years of research and experience as well as from ongoing research we know that some chemotherapy drugs work better against certain cancers than others. Modern treatment protocols use that knowledge by combining the most effective known drugs in a certain order to achieve the fastest and maximal destruction of cancer cells (combination chemotherapy). Chemotherapy drugs can be used alone or in combination with other drugs. They can be given directly into the blood stream through a vein (intravenously or "IV") or through a central venous catheter. They can also be given orally, by injection into the muscle ("intramuscularly" or "IM"), by injection under the skin ("subcutaneously", SC, or SQ), or by direct placement on the skin ("topically"). Chemotherapy can also be injected into the spinal fluid "intrathecally" (IT).
Chemotherapy is sometimes used together with other treatments; at other times it can be used alone. It can be given in the hospital, at the doctor's office/clinic, or even at home, depending on the complexity of the drug combination. The frequency of chemotherapy depends very much on the type of cancer, the goals of treatment, the specific drugs used, and the patient's response to treatment. Chemotherapy is usually given in cycles of intense treatment followed by rest periods that give the body's normal cells a chance to repair themselves or make healthy new cells, and enable the patient to regain strength. The treatment schedule is very important for the drugs to work correctly so if doses are missed at home, the doctor should always be notified. On occasion, the doctor may need to delay treatments because of low blood cell counts or other complications. If that happens, you will be instructed what to do while waiting for therapy to resume.
Chemotherapy achieves three main goals:
Chemotherapy is often used in combination with other treatments for additional goals:
- It kills cancer cells in order to cure the patient
- It controls the cancer and prevents its spread throughout the body
- It relieves symptoms (pain, anemia, thrombocytopenia, etc)
Like any medication, chemotherapy has potential side effects; these will be discussed at length before treatment begins. It is important to remember that not all patients suffer all of the side effects listed for a given drug and not all patients sustain these side effects to the same severity. Many chemotherapy drugs affect the rapidly dividing normal cells in our body. However, it is expected that normal cells will eventually repair themselves or be made anew, while cancer cells that lack that self-repair ability, will die.
- Decreasing the tumor size before surgery or radiation therapy (neo-adjuvant chemotherapy).
- Killing any cancer cells that may be left over after surgery and/or radiation therapy (adjuvant chemotherapy).
- Enhancing radiation therapy and other therapies.
- Trying to destroy cancer if it comes back or has spread to other parts of the body.
Examples of rapidly dividing cells that are harmed during chemotherapy include:
In addition, there are many other side effects (not related to rapidly dividing normal cells) that are specific to each medication and will be discussed at length before chemotherapy is initiated. Examples of other side effects include:
- Bone marrow cells - the bone marrow is the soft material in the center of bones. It is the "factory" that has cells (called stem cells) that give rise to red cells, white cells and platelets for our blood. Those stem cells divide and mature rapidly in order to replenish diminished blood cells. When chemotherapy affects these stem cells, it decreases the production of red cells (anemia), white cells (neutropenia), and platelets (thrombocytopenia).
- Hair cells - hair cells, also called follicles, divide rapidly as well (that is why we need haircuts every so often). Chemotherapy stops this division, causing the old hair to fall out, resulting in baldness. Hair always grows back after chemotherapy ends (and sometimes even during periods of milder chemotherapy).
- Gastrointestinal cells (especially cells lining our mouths) - chemotherapy damages those cells and can result in mouth sores (also known as mucositis)
- Reproductive cells - certain chemotherapies can lead to temporary or permanent damage of the testicular cells that produce sperm in males and the eggs in females. The doctor will discuss that risk before chemotherapy starts.
Finally, children who undergo chemotherapy are also known to be at risk of developing a second cancer later in life. The risk is very small but cannot yet be estimated accurately because treatments for childhood cancer only began showing their effectiveness less than 30 years ago. This risk depends largely on the type of chemotherapy drug used, as well as additional components of treatment, particularly radiation. Whenever possible, doctors try avoiding treatments that have been associated more frequently with the risk of future secondary cancer or other long-term side effects.
- Nausea, with or without vomiting
- Numbness and tingling of the hands and feet
- Heart damage
- Liver damage
- Hearing loss (temporary, partial, or complete)
- Kidney damage
Many of the side effects of chemotherapy can be prevented, treated, or ameliorated. For example:
- We now have very effective medications to prevent nausea and vomiting
- We can treat mouth sores better than in the past
- We can avoid or treat constipation efficiently
- We are better able to treat pain
- We prevent the symptoms of anemia with red blood cell transfusions (and sometimes by giving a medication that stimulates the bone marrow to make red blood cells somewhat faster), and prevent the symptoms of thrombocytopenia with platelet transfusions
- We can stimulate the bone marrow to make white blood cells somewhat faster, limiting the risks of infection
- We can dramatically reduce the chance of fungal infections and certain pneumonias (especially Pneumocystis carinii pneumonia, also know as PCP) with antibiotics
- We now have a wide choice of very effective antibiotics and anti-fungal agents to treat infectious complications
- We can protect the heart from a chemotherapy drug known to be harmful by using a protective agent along with the chemotherapy
- We can refer teenage male patients to sperm banks when we use medications known to result in sterility in order to harvest, freeze and preserve normal sperm cells before treatments starts
- Various hair replacement services are available for those with significant hair loss
- We use combinations of chemotherapy drugs that do not share the same side effects so as to avoid doubling the risk for the specific side effects
- We allow rest periods for the body and normal cells to recuperate before the next cycle of treatment
- We often modify the dosage of a medication that proves to be particularly toxic to a given patient and, on rare occasions, eliminate that drug altogether from the treatment protocol
- And finally, we seek out newer and more effective ways to avoid or treat side effects based on ongoing published research.