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Improved DNA sequencing helps leukemia treatments

Tue., May 7, 2013, midnight

ST. LOUIS – Doctors can now view patients’ leukemia from the equivalent of a helicopter instead of an airplane with new DNA sequencing of cancer cells, an analogy described by Richard Wilson, director of Washington University’s Genome Institute.

The researchers led by Washington University studied the genetic profiles and mutations of 200 patients in St. Louis with acute myeloid leukemia, a blood cancer that can spread fast and is difficult to treat.

An average of 13 mutated genes were found in each patient’s cancer cells, which could give doctors a road map for how aggressive a patient’s cancer is and which drug might work best. As genetic coding becomes more accessible to cancer treatment centers, each patient could be tested for hundreds of dollars. Ideally, the coding could help doctors predict which patients would benefit from risky and expensive bone marrow transplants.

The scientists found the mutations by sequencing the DNA of cancer cells and healthy cells in each patient with leukemia. Other cancers such as breast and lung tumors that have been studied through the Cancer Genome Atlas project have turned up several hundred mutations, creating the potential for more complex and individualized treatment plans. Wilson said the large number of patients in the study means scientists have likely found most mutations that occur in this type of leukemia.

The cancer atlas has helped push the prevailing scientific theories away from defining a tumor by the organ it attacks, and more by its genetic code. Some patients’ lung tumors more closely resemble others’ breast tumors, and they would benefit from the same drug. But most cancer drugs are only approved for specific cancers, and insurance companies won’t always pay for an unapproved treatment. The work now moves toward persuading oncologists to think more globally about cancer, and to allow for more flexibility in treatment and payment options.

Each year about 15,000 people in the U.S. are diagnosed with acute myeloid leukemia and more than 10,000 die from the disease. Many patients do not respond to traditional chemotherapies, indicating the need for better drugs. Others can benefit from bone marrow transplants early in the course of the disease, but it has been difficult for doctors to predict which patients are candidates. The genetic sequencing can help doctors put patients in more appropriate treatment protocols.

“In no way does it explain everybody’s disease,” Wilson said. “Ideally you’d like to find a single smoking gun for a particular disease, and a magic bullet that allows you to treat that disease. Now we kind of have a playbook for more precise treatment that has a better chance of working.”

The research was funded by the National Institutes of Health and was published Wednesday in the New England Journal of Medicine.

Tags: DNA, leukemia

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