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Chemotherapy gets personal for cancer patients
U-M researchers evaluate more effective way to determine the best chemotherapy dose for breast cancer patients
originally posted October 1, 2001
ANN ARBOR, Mich. - Chemotherapy has long been known to be an effective way to control the spread of cancer. But its benefits don't come without the price of possible devastating side effects including hair loss and fatigue. Sometimes without warning, even more serious side effects can happen which result in illness and hospitalization. Now, a new study may have found a way to eliminate the unpredictability of chemotherapy without jeopardizing the treatment.
Physicians at the University of Michigan Health System's Comprehensive Cancer Center are conducting a study on chemotherapy doses for breast cancer patients. This population, according to Anne Schott, M.D., medical oncologist at the Cancer Center and assistant professor of hematology/oncology, often has chemotherapy prescribed to them as a form of treatment.
"For a woman who has just been diagnosed with breast cancer, her treatment options include chemotherapy, as well as surgery, hormonal therapy, and radiation treatments," she says. "But to control the cancer spreading, usually most cases require chemotherapy."
Chemotherapy is the treatment of cancer with drugs that can destroy cancer cells. The body, usually the liver or the kidneys, breaks down the medication. The amount of chemotherapy given is most often based on a patient's height and weight. But this method does not always lead to the best dose for patients.
"Schott explains, "The problem with that approach is it doesn't take into account an individual's metabolism of chemotherapy, which could vary greatly depending on what medicines they are on, what their heart function is, what their liver function is, and what their kidney function is."
Researchers at the Cancer Center are trying to fix the problem by tailoring doses with results from the Erythromycin Breath Test, a test - originally developed at the U-M - that can determine how a patient's body breaks down the antibiotic erythromycin. Erythromycin is metabolized in the same way as many chemotherapy drugs, by the enzyme CYP3A4.
"We're using the Erythromycin Breath Test to tell us how fast an individual will metabolize other drugs that use the same enzyme," she says. "In the study we're conducting, we're looking at the breast cancer drug Taxotere, which uses that same enzyme, to tell us how to dose the chemotherapy drug.
The Erythromycin Breath Test works like this. The patient gets an injection of a very small and safe amount of radioactive erythromycin. After they get the injection, they wait 20 minutes for the drug to be metabolized and then they blow air out into a bag. From there, doctors can measure traces of carbon dioxide in their breath. Carbon dioxide is one of the chemicals produced when erythromycin is broken down by the body.
"By using the Breath test, we can actually pick a dose of Taxotere that's specificfor the individual, not just based on their height and weight," Schott notes. "By picking a dose that's specific for the individual, we will not have the risk of either overdosing or underdosing the individual."
This is very important since chemotherapy drugs can harm healthy cells, causing side effects. With the use of tailored doses of chemotherapy drugs, it is hoped that patients will be less likely to experience those side effects.
Some study participants have already reported a positive effect. Gretchen Davenport was diagnosed with breast cancer in 1998. When it came back a year later, she enrolled in the Cancer Center study."In my first run of chemotherapy almost 4 years ago, I was very tired and had to have Neupogen," Davenport says. "But the cancer came back and I had to have chemotherapy again, so I came here to the Cancer Center. This time I had very few side effects. I wasn't tired and never lost my appetite."
Preliminary results show that tailored dosing allows doctors to achieve more consistent drug levels in the body, compared to just giving everyone the standard dose. Consistent drug levels are critical in fighting cancer cells. "We think it's very important to make sure we're still seeing the same effectiveness of the drug in the tailored dosing as we would if we gave the standard dose," Schott notes.
Schott says although the drug Taxotere is being testing in the current study, other chemotherapy drugs are not being ruled out. "We've chosen Taxotere as really a proof of principle that this sort of tailoring will work," Schott says. "Once this study is completed, we will expand to include drugs which have the same kind of metabolism."
Gretchen Davenport hopes all women suffering with breast cancer can some day take advantage of tailored chemotherapy dosing. "I think it's wonderful what they can do," she says. "It makes you feel a lot better about getting chemotherapy, that you're getting a dose that's specifically for you."
The study at the Cancr Center has already shown promise on a small group of breast cancer patients. Currently, researchers are enrolling women with breast cancer who would benefit from Taxotere. For more information on the tailored dosing study contact the UMHS Cancer AnswerLine™ at 1-800-865-1125.
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