Doctors currently use surgical biopsies to diagnose cancer and identify the best available treatments but such biopsies are painful and expensive. There are also some instances when tissue samples are difficult to get or are not enough for genomic testing.

A new test, however, may give doctors and patients an alternative at probing cancerous tumors. Researchers on Saturday reported about the results of the largest study to date of a new blood test that can detect and analyze cancer.

They concluded that the so-called liquid biopsies — which involve doctors using blood taken from a patient's arm to analyze DNA that tumors shed into the bloodstream — offer a reliable, cheaper and less invasive alternative to conventional tissue-sampled biopsies.

For the study, which was presented at American Society of Clinical Oncology (ASCO) annual meeting in Chicago, researchers involved more than 15,000 patients with breast cancer, advanced lung cancer, colorectal cancer and other tumors to see how liquid biopsies fare against tissue biopsies.

Philip Mack, from the University of California, Davis, and colleagues compared the results of liquid biopsies with data from published results of cancer patients and found that the blood tests identified the same cancer genes associated with those cancers 87 percent of the time.

"The overall accuracy of ctDNA [circulating tumor DNA] sequencing in comparison with matched tissue tests was 87 percent (336/386)," the researchers reported. CtDNA is a biological-chemical marker that hints at the presence of cancer cells in the body. The chemical marker is leeched into the blood vessels.

The researchers also looked at the results of traditional biopsies that used physical samples of the cancer-afflicted tissues within six months of the blood-based test and found the same results on genetic mutations in nearly all of the cases.

"The accuracy increased to 98 percent when blood and tumor were collected less than six months apart," the researchers added.

The study results hint at the potential of liquid biopsies in cancer diagnosis. It likewise shows that for some patients, blood-based biopsy could be a better alternative compared with traditional methods that use tissue cultures.

"We have lots of older or less healthy patients who simply are not great candidates for surgery," said Joshua Brody, from Mount Sinai's Tisch Cancer Institute in New York City. "For them, it's not this [liquid biopsy] versus tissue biopsy. It's this versus nothing."

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