DNA Mapping May Lead to Personalized Cancer Treatment

Technique helped determine lymphoma patients' prognosis, researchers report

By Mary Elizabeth Dallas

Wednesday, November 9, 2016

WEDNESDAY, Nov. 9, 2016 (HealthDay News) -- DNA sequencing may help personalize treatment for people with lymphoma, a new study suggests.

By analyzing small bits of DNA in the blood, researchers at Stanford University School of Medicine said they could determine the cancer's subtype. They said they could also identify mutations that might make treatment less effective or worsen a patient's prognosis.

The study authors said their findings add to growing evidence that noninvasive, blood-based biopsies may help detect cancer earlier by tracking its evolution. They said this test may also significantly change how the disease is treated.

"Now we can identify the subtype of the tumor, watch how it changes over time and begin to tailor our chemotherapy choices based on the presence or absence of specific mutations," said study co-senior author Dr. Ash Alizadeh, an assistant professor of medicine/oncology.

"We've moved beyond just measuring disease burden based on the amount of tumor DNA in the blood," Alizadeh said in a university news release.

The study included 92 people. They all had a common form of non-Hodgkin lymphoma known as diffuse large B-cell lymphoma. The disease is biologically diverse. That means patients with this disease tend to respond very differently to treatments, the researchers explained.

Roughly one-third of those with the disease relapse, or develop treatment resistant tumors, the researchers said. The researchers also said that some people with mild, slowly progressing forms of the disease may suddenly develop aggressive cancer.

Using an advanced DNA sequencing technique, the research team pinpointed circulating tumor DNA in samples of the patients' blood. They compared these results with previous blood samples that were taken from the patients, as well as blood samples of tumor cells from invasive biopsies.

"This transformation is very difficult to detect, and usually requires an invasive biopsy to diagnose," said study co-senior author Dr. Maximilian Diehn. He's an assistant professor of radiation oncology at Stanford.

"Our approach will allow us to monitor patients over time with a simple blood test, and may help us identify transformation much earlier," Diehn said.

The study showed that low levels of circulating tumor DNA before treatment began were associated with progression-free survival. Higher levels of tumor DNA were linked with a worse overall disease outlook.

The researchers said they were able to detect the cancer's presence in the blood of patients who were relapsing six months before any symptoms appeared. In some cases, the blood test was able to predict a recurrence up to 2.5 years before symptoms appeared, the researchers said.

The study's authors said they were also able to use this DNA sequencing technique to figure out the type of cell from which the cancer originated. This helped the researchers predict a patient's prognosis. The researchers said they could also predict which patients would develop aggressive lymphoma even before symptoms were seen.

"In this study we've shown five distinct ways -- by quantifying tumor burden, identifying disease subtype, cataloging mutations, predicting transformation and providing early warnings of recurrence -- that circulating tumor DNA can yield potentially clinically useful information," Diehn said.

"Now we're eager to conduct prospective studies in recently diagnosed patients to learn how we can best improve patient care," he added.

The study was published Nov. 9 in Science Translational Medicine.

SOURCE: Stanford University School of Medicine, news release, Nov. 9, 2016

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