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DNA sequencing may help personalize cancer treatment
November 29, 2016, 1:36 pm

Researchers behind a new study say that by analyzing small bits of DNA in the blood, they are able to determine a cancer's subtype. They were also able to 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 co-authors behind the study report.

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, which means that patients with this disease tend to respond very differently to treatments.

Roughly one-third of those with the disease relapse, or develop treatment resistant tumors, the researchers said. They added 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. The new approach will allow doctors to monitor patients over time with a simple blood test, and may help them identify transformation much earlier.

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.

Through their study the researchers showed five distinct ways — by quantifying tumor burden, identifying disease subtype, cataloging mutations, predicting transformation and providing early warnings of recurrence — that circulating tumor DNA could yield potentially clinically useful information.

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