By using cells donated by a woman in her 50s who died of leukemia, the scientists at the Washington University sequenced DNA from her cancer cells and compared it to the DNA from her own normal, healthy skin cells. The study, published on Wednesday in the journal Nature, marks the first time scientists have decoded the entire genome of a cancer patient, identifying a series of genes never before linked to the type of white blood cell cancer that the woman suffered from.

Acute Myelogenous Leukemia (AML) has a 5 year survival rate of approximately 20% and kills about 8,000 people every year in the U.S.A. The symptoms of AML are caused by replacement of normal bone marrow with leukemic cells, resulting in a drop in red blood cells, platelets, and normal white blood cells. These symptoms include fatigue, shortness of breath, easy bruising and bleeding, and increased risk of infection. Although several risk factors for AML have been identified, the specific cause of AML remained unclear until today. As an acute leukemia, AML progresses rapidly and is typically fatal within weeks or months if left untreated.

In the study researchers compared tumor cells and normal, healthy cells all donated from the woman who died of leukemia. The comparison allowed them to identify mutations that occurred only in the cancer cells. None of the researchers knew what to expect for the number of mutated genes in the cancerous cells. “We were flying blind,” says study coauthor Timothy Ley. They finally identified 10 significant mutations that appeared to encourage tumor growth and allow the cells to fight off chemotherapy; eight of those mutations had never before been linked to leukemia. Apart from this researchers also studied tumor samples from 187 other patients with the same form of leukemia.

Previous research had linked two of the 10 identified mutations to AML, but the rest never before had been implicated. "The other eight were all things that caught us off guard. They're all new. And they are all in genes that we didn't really have on our radar for this particular kind of cancer. In retrospect, they all make sense," Ley said.

This research is likely going to lead to new treatments, and a better understanding of the diseases. The hope is that by being able to figure out the genome of the cancer patient, they will now be able to move forward with more advanced treatments that can be more personalized depending on the patient.

Geneticist Dr. Francis Collins, a former director of the U.S. National Human Genome Research Institute, told the BBC the study a "true landmark in cancer research.” The findings will not help patients immediately, but researchers say they could lead to new therapies and will almost certainly help doctors make better choices among existing treatments, based on a more detailed genetic picture of each patient’s cancer.