Chemotherapy is the use of potent drugs or chemicals, often in combinations or intervals, to kill or damage cancer cells in the body. Chemotherapy drugs are often called anticancer agents. The drugs must be toxic enough to kill leukemic cells, which is why chemotherapy can be hard on your body; the drugs' toxicity can harm your healthy cells as well. However, successful chemotherapy depends on the fact that cancerous cells are more sensitive to the chemicals in the drug than normal cells are.
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. Today's treatments for leukemia, lymphoma and myeloma sometimes combine chemotherapy with radiation therapy. Very high dose chemotherapy followed by stem cell transplantation can also be used.
The goal of chemotherapy is to damage or kill cancer cells so there's either no sign of illness (remission) or the disease's progress is slowed. Chemotherapy can produce long-term remission or outright cure for many persons, depending on the cancer type and its extent.
How Does Chemotherapy Work?
Normal, healthy cells divide and grow in a controlled pattern. As each cell divides, a replica is produced. Cancer cells, on the other hand, grow uncontrollably and rapidly with no pattern. When a cancer cell comes into contact with a normal cell, the cancer cell takes over and copies itself many times, overburdening the body with cancer cells.
All chemotherapy drugs interfere with cancer cells' ability to grow or multiply. Different groups of drugs harm cancer cells in different ways. That's why it's essential that the disease be accurately diagnosed: Certain chemotherapy drugs are used only for certain disease cell types.
Attacking DNA and RNA
Both new chemotherapy drugs and new ways to attack cancer cells continue to emerge as research progresses. Many chemotherapy drugs attack cancer cells by interacting with the cancer cell's DNA or RNA (genetic makeup). This interaction changes the DNA in such a way that it kills the cancer cell or prevents it from growing or dividing. Chemotherapy drug types that act directly to impair DNA include:
- DNA-damaging agents. These drugs, referred to as alkylating agents, damage the DNA so severely that the cancer cell is killed. Examples of alkylating agents are chlorambucil (Leukeran®), cyclophosphamide (Cytoxan®) and melphalan (Alkeran®). Other DNA-damaging agents, such as carboplatin (Paraplatin®), attach to the DNA and prevent the cancer cell from growing.
- Antitumor antibiotics. By inserting themselves into a cancer cell's DNA, these drugs prevent the DNA from functioning normally and often kill the cancer cell. Examples are daunorubicin (Cerubidine®), doxorubicin (Adriamycin®, Doxil®), idarubicin (Idamycinv®) and mitoxantrone (Novantrone®).
- Antimetabolites. These drugs mimic the substances that the cancer cell needs to build DNA and RNA. When the cancer cell uses the antimetabolite instead of the natural substances, it can't produce normal DNA or RNA and the cell dies. Examples are methotrexate (Rheumatrex®, Trexall®), fludarabine (Fludara®) and cytarabine (cytosine arabinoside, ara-C, Cytosar-U®).
- DNA-repair enzyme inhibitors. 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. These agents attack the cancer cell proteins that normally repair DNA damage. Examples are etoposide (VP16, Etopophos®, Toposar®, VePesid®) and topotecan (Hycamtin®).
Other Modes of Attack
- Hormones such as prednisone and dexamethasone (Decadron®) in high doses can kill lymphoma or lymphocytic leukemia cells.
- Antimitotic drugs such as vincristine (Oncovin®) or vinblastine (Velban®) damage cancer cells by blocking a process called mitosis (cell division), preventing cancer cells from dividing and multiplying.
- Antibodies made specifically to attach to cancer cells interfere with a cancer cell's function and kill the cell. Some antibodies are combined with a toxin or radioactive substance.
For information about the drugs mentioned on this page, visit Drug Listings.
How Are the Drugs Given?
The drugs can sometimes be swallowed in pill, capsule or liquid form. But in most cases, you'll receive the drugs through a catheter, or central line — a small device that's placed in one of your veins, usually in your upper chest, by making a small surgical incision. The catheter can stay in place for weeks or months.
Your doctor or nurse uses the catheter — a thin, flexible tube or intravenous (IV) line — to deliver the drugs directly into your bloodstream. Using a catheter instead of repeatedly inserting an IV needle can help ward off infection and irritation and may be more comfortable.
Two Treatment Phases for AML and ALL
Most patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia(ALL) usually receive treatment in two phases, or cycles:
- Induction therapy
- Post-remission, or consolidation, therapy
The first phase of AML and ALL chemotherapy is induction therapy. AML and ALL patients need to start induction therapy right away. The goal of induction therapy is to "induce," or encourage, remission — when no evidence of the disease is left. Specifically, induction therapy attempts to:
- Kill as many AML and ALL cells as possible with chemotherapy
- Get blood counts back to normal
- Rid the body of all signs of disease for an extended period
Patients may have to go through several rounds, or cycles, of induction therapy before all the leukemic cells are destroyed. Doctors know induction therapy is successful when they can't see leukemia cells in blood or marrow. Patients also start to feel better. This is what's known as being in remission.
Induction therapy is done in a hospital, where most patients will spend four to six weeks undergoing several cycles of chemotherapy. Generally, a cycle of chemotherapy consists of a week of receiving the drugs followed by several weeks to let the body recover. Patients who have a full-time caregiver and live near the treatment center may be discharged sooner, depending on the center's policies and the patient's health status.
Once patients complete induction therapy and enter remission, they still need additional therapy. This second phase of treatment is called post-remission therapy, or consolidation therapy. Without this second step, the cancer will likely return.
Post-remission therapy includes chemotherapy and sometimes a stem cell transplant. Its purpose is to destroy the stray leukemic cells not found by blood or marrow tests. Patients undergo post-remission therapy in the hospital or an outpatient setting over a period of four to six weeks, sometimes longer, depending on the post-remission treatment and its side effects.
To determine the type of post-remission therapy patients need, doctors consider:
- Overall health
- Certain types of changes to the genes in leukemic cells
- The availability of a stem cell donor
Patients who don't undergo stem cell transplantation are generally given four cycles of chemotherapy. For best results, intensive chemotherapy is given with high doses of cytarabine or other drugs.
Maintenance Therapy for ALL
Patients who have ALL need a longer period of post-remission therapy than AML patients do. Their continued therapy after the initial post-remission therapy is called maintenance therapy and lasts for about two years.
Overcoming Anxiety About Chemotherapy
Having to make choices about chemotherapy and other treatment options can cause a great deal of anxiety. Asking your doctor any questions you have may ease stress and give you some sense of relief in making these choices. In addition, your nurses, social workers and other health professionals understand the complexity of the emotions and ongoing needs of what you're enduring. They're available to spend time with you, answer questions, lend emotional support and provide referrals to other useful resources. Visit National Cancer Institute, Chemotherapy and You for more.
Taking Medications at Home
You may sometimes be able to take chemotherapy drugs at home. Before starting your regimen, ask your doctor these questions so you thoroughly understand how you're supposed to take the drugs and what to do if problems arise:
- What if I miss a dose?
- What if I vomit immediately after taking my medication?
- Is it safe to drink alcohol during my use of this drug?
- When should I take the medication?
- How should I store it?
- Do I need to take this drug with food?
- When and how should I contact the healthcare team with questions?
- How do I contact a healthcare professional after hours?