For cancer patients undergoing treatment, liquid biopsies could spare them some of the painful, expensive and risky tissue tumor biopsies and reduce reliance on CT scans, which must be limited because of the danger posed by overexposure to radiation.
With patients for whom physicians cannot get a tissue biopsy — e.g. some lung cancer patients with tumors too dangerously close to arteries or the heart — the liquid biopsy could prove a safe and effective alternative that could help determine whether treatment is helping eradicate the cancer.
"We can actually do it without even looking at the tumor," Velculescu said. "We can just look at the blood."
However, experts caution that more studies are necessary to determine the accuracy of the test, precisely which cancers it can detect at what stages and whether it improves care or survival rates.
Early research on the liquid biopsy has focused heavily on patients with later-stage cancers who have undergone treatments, including chemotherapy, radiation, surgery, immunotherapy or drugs that target molecules involved in the growth, progression and spread of cancer. The tests can quickly assess the effectiveness of surgery or other treatment, while traditional biopsies and CT scans can still remain inconclusive as a result of scar tissue near the tumor site.
"You could actually follow how your tumor is growing or shrinking while you're on a certain therapy," Velculescu said. "And you could use that to determine whether the therapy's working or whether you should switch to another therapy."
DNA fragments are found in relatively high concentrations in the blood of most patients with metastatic cancer and at much lower, but detectable, concentrations in a substantial fraction of patients with localized cancers.