Toward Blood-based Cancer Detection

from The Scientist by Jyoti Madhusoodanan

Circulating tumor cells, exosomes, and DNA can improve the diagnosis of many cancers. But are liquid biopsies ready for prime time?

While the detection of solid tumors remains routine procedure in cancer diagnostics, modern technologies such as next-generation sequencing have enabled scientists to track cancer beyond its tissues of origin and in greater detail. Many tumors shed stray cells, vesicles called exosomes, and traces of DNA into blood and other body fluids. Recent research has shown that such debris can serve as markers to monitor disease progression—and even help researchers diagnose cancers before symptoms appear.

Tumor DNA, it turns out, can be detected in routinely drawn blood samples. In a study published last month (June 5) in JAMA Oncology, for example, researchers who examined blood samples from more than 4,000 pregnant women—drawn for the purpose of identifying chromosomal abnormalities in the fetus—identified three cases of maternal cancers: an ovarian carcinoma, one follicular lymphoma, and a Hodgkin lymphoma. “In the majority of these tumors, even low grade ones, we found we could use an individual’s blood as a surrogate for studying tumor biology,” said study coauthor Joris Vermeesch of the KU Leuven Center for Human Genetics in Belgium.

Such “liquid biopsies” are not unique to blood and plasma samples. In other studies, researchers have correlated the risk of bladder cancer recurrence to methylated DNA levels in urine, detected bowel cancer DNA in stool samples, and identified cancer-linked mutations in the saliva of patients with head and neck carcinomas. Previously, such molecular tests were used to monitor advanced disease and metastasis. Now, with increasingly precise tools, small amounts of cancer cells and DNA can be identified in blood even in the earliest stages of disease.

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