Living with Leukemia : Treatment

by Food and Drug Administration (FDA)

(Page 2 of 3)

Many people died from leukemia — often within months of diagnosis — before the advent of effective treatments. Now, many more are cured (usually defined as five or more years of disease-free survival).

The goal in treating leukemia is to achieve complete remission (all signs and symptoms of leukemia have disappeared, although there still may be cancer in the body) by destroying cancerous cells so that normal cells can again grow in the bone marrow. In remission, cancerous cells cannot be seen in the blood or bone marrow, but more therapy is needed to achieve a cure. Several areas of research have yielded new approaches to treating leukemia. But the kind of treatment given and the outlook for a person with the disease vary greatly, according to the exact type of leukemia the person has, and other individual factors.

Chemotherapy refers to the use of drugs to kill cancer cells. It is the main treatment for nearly all types of leukemia. Most of these anticancer drugs are injected through a vein (IV injection or intravenously), but some can be taken by mouth. Either way, the drugs enter the bloodstream and spread throughout the body to kill cancerous cells.

Chemotherapy is given in cycles: a treatment period is followed by a recovery period. The process may be repeated. The duration of the treatment varies depending on the type of leukemia. Sometimes certain drugs are combined with others for a greater treatment effect. Unlike many people who show progress following chemotherapy, Keller periodically showed progress, but then relapsed.

"Neil responded well to chemotherapy for short periods of time," says Kathy Keller, "but he never went through a remission."

Most anticancer drugs are cytotoxic, which means they kill not only cancerous cells but also normal cells, particularly in the bone marrow. "The rationale of chemotherapy is that the normal cells are more likely to eventually survive the effects of chemotherapeutic agents than the cancer cells," says Amna Ibrahim, M.D., a medical officer in the FDA's Center for Drug Evaluation and Research.

New Treatments

Gleevec demonstrated in trials that it substantially reduces the level of cancerous cells in the bone marrow and blood of people with CML. A new class of drug to fight cancer, Gleevec is different from other cancer drugs because it specifically targets an enzyme that causes cells to become cancerous and multiply in people with CML. It works by blocking the protein product that is responsible for transforming normal cells into cancerous ones. Gleevec provided a new cancer treatment for chronic CML after the failure of interferon-alpha therapy, CML in blast crisis, and CML in an accelerated phase.

After two years of study, Gleevec, manufactured by Novartis Pharmaceuticals Corp., of East Hanover, N.J., appears to offer advantages over some other leukemia treatments: oral administration, tolerable side effects, and a high response rate.

The FDA's accelerated approval of Gleevec was based on the response rate observed in early clinical trials. Accelerated approval allows products for serious or life-threatening illnesses to reach the market sooner, based on clinical trials that have not yet demonstrated true clinical benefit, like survival or improved disease-related symptoms, but in which early results have indicated the drug is reasonably likely to have real clinical benefit.

James Foran, M.D., a medical oncologist at the University of Nebraska Medical Center and spokesman for the Leukemia and Lymphoma Society, says that CML occurs when pieces of two different chromosomes break off and reattach on the opposite chromosome, forming what's known as the "Philadelphia chromosome." This chromosome "translocation" leads to the enzyme being "turned on" all the time. As a result, potentially life-threatening levels of both mature and immature white blood cells occur in the bone marrow and the blood. "Gleevec shuts down the growth signals from the Philadelphia chromosome," says Foran, and blocks the rapid growth of malignant white blood cells.

But because the information from Gleevec clinical trials is still early, it is not known how durable the responses to this treatment will be. In fact, relapses following initial responses to Gleevec are now being reported.

Another class of drugs, known as differentiating agents, is used in treating APL. These drugs promote differentiation of the very immature leukemic white blood cells into more mature functioning cells. Two drugs in this class include Vesanoid (all-trans retinoic acid or ATRA), made by Hoffmann-La Roche Inc. of Nutley, N.J., which was approved by the FDA for first-line treatment, and Trisenox (arsenic trioxide), made by Cell Therapeutics Inc. of Seattle and approved for second-line therapy after ATRA treatment failure. These drugs have improved the prognosis of APL.

Mylotarg (gemtuzamab ozogamicin), another new type of leukemia drug, consists of an antibody against AML blast cells combined with a toxin to kill the cells. Mylotarg, manufactured by Wyeth-Ayerst Pharmaceuticals of St. Davids, Pa., the pharmaceutical branch of American Home Products Corp., was approved in May 2001 for treatment of elderly patients with AML who cannot tolerate more conventional chemotherapy.

About the Author

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