Results of their large 202-patient study, presented at the annual meeting of the American Society of Clinical Oncology, demonstrate a complete remission rate of 69 percent, the highest rate ever achieved, the researchers say.
"The study has been accruing patients over a four year period. Not only are the remissions very frequent and of a long duration, in almost half of the responding patients we can't find any evidence of disease using the most sensitive techniques available," says lead investigator, Michael Keating, M.D., professor in the Department of Leukemia.
"I am most optimistic about this combination therapy, and it is now the cornerstone of treatment at M. D. Anderson for our patients with this leukemia, both as initial treatment and when previous treatment has failed," Keating says.
Chronic lymphocytic leukemia (CLL), a cancer of the blood, is the second most commonly diagnosed type of leukemia. It is caused by the overproduction of immature blood cells in the bone marrow which crowd out healthy cells needed to fight infection and deliver oxygen to the body. CLL progresses slowly, and it may take years for symptoms to appear or for treatment to be needed.
Typically, chemotherapy is used to treat the cancer, but with limited success. This clinical trial was the first major study using a combination of two chemotherapy drugs (Fludarabine and Cyclophosphamide) with Rituximab, a monoclonal antibody drug that has been federally approved for use in non-Hodgkin's lymphoma.
Monoclonal antibodies are designed to hook onto proteins found on the surface of cancer cells and trigger an immune response against the cells. According to Keating, the combination is usually given to patients outside of the hospital and makes leukemia cells more sensitive to the effects of chemotherapy. "It is clear that Rituximab is adding significantly to treatment.”
"This appears to work in all age groups and in all stages of the leukemia," he says. "Even patients older than age 70 have a response rate of more than 80 percent with 40 percent to 45 percent achieving a complete remission, which was formerly uncommon in this age group."
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