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April 20, 2011

Human Genome Sequencing Helps Doctors Determine Treatment

by Art Chimes

New developments show the promise of personalized medicine

Sequencing the human genome - making a detailed map of all of a person's genes - is less than a decade old. The technology brings with it the promise of personalized medicine. Now, scientists are reporting some of the first cases of medical decisions based on information from sequencing the patient's entire genome.

The patient had leukemia. But there were some inconsistencies in the biopsy. In that case, the usual procedure is to go with the more aggressive therapy - here, a bone marrow transplant.

Richard Wilson heads the Genome Center at Washington University in Saint Louis, whose doctors treated the leukemia patient.

"When the patient was referred here for a bone marrow transplantation, her physician thought, you know, this is a case where I think we can go deeper," he says. "I think that the genome-sequencing technology that we're doing here at Washington University is mature enough, that we could actually apply it to this case. And we could make sure that this is a patient who really needs the bone marrow transplant, and couldn't just be treated with a particular drug."

In fact, the genetic sequencing identified an abnormality that can be effectively treated by a drug, and the patient's leukemia is now in remission.

Wilson is co-author of two papers in the journal of the American Medical Association, JAMA, describing how doctors used information gleaned from sequencing a patient's genome.

In the second case, the patient died at age 42 after a series of different cancers. After her death, her whole genome was sequenced and showed a mutation in a gene that is important in suppressing tumors.

"The concern is that it could also be a mutation that could be passed on to her children," Wilson says. "And through the nature of the mutation and understanding the gene, we thought that this might be information that might be very useful to their family physician. You know, if a physician is armed with that information, they are going to suggest that, for example, a young woman might want to have more aggressive breast cancer screening."

Although whole-genome sequencing provided useful information for doctors in these cases, Wilson says much more needs to be done on the research side - in particular, a lot more cancer-patient sequencing to better understand what has gone wrong, and what to do about it.

"And I expect that the ability to actually do that and have it not be a ridiculously expensive endeavor, is not that far in the future," he says.

Cancer specialist Boris Pasche of the University of Alabama at Birmingham says it all depends on how much cheaper the procedure gets.

"The costs of whole-genome sequencing have decreased by 100-fold in barely two years and a half. If we assume that there will be continuous decrease in the cost of this technology, then within the next five years it could be conceivable that any if not all new cancer patients could be assessed with this technology."

Pasche comments on this potential new tool in a JAMA editorial. He calls cancer treatment the "first test bed" for genome-based personalized medicine. Washington University's Richard Wilson says other candidates for this approach include diabetes and various neurological disorders.