Blood Test Detects Cancer Early, But Has Some Holdups

A blood test has detected cancer in individuals who had no history or symptoms of cancer. A trial of the test, which is still experimental, shows that it is possible to identify signs of cancer early on, long before people show symptoms of being sick. But the study also identified some people as having cancer when, in fact, there were no tumors at all, and it missed some cases of cancer, researchers reported yesterday (April 28) in Science and at a virtual session of the American Association for Cancer Research meeting.

“This [test] is not at the place where it could be used today,” Len Lichtenfeld, the deputy chief medical officer for the American Cancer Society, tells the Associated Press. “It will need many more studies to demonstrate value,” including whether it improves survival, he adds.

The test, which analyzes blood for DNA released by tumor cells as well as for known protein biomarkers of specific cancers, accurately detected undiagnosed cancers in 26 women of the nearly 10,000 women aged 65 to 75 who participated in the study. They were diagnosed with a range of cancers, from breast, uterine, ovary, and kidney tumors to lymphoma. There were 24 women who had tumors that weren’t detected by the test; their breast, lung, and colon cancers were identified by other screening methods. Another 46 women had cancer that was eventually identified when they developed symptoms or by imaging unrelated to cancer screening, but not by the test. In addition, 101 women had a positive blood test, but no cancer was identified during follow-up imaging.

Even with the false positives and missed cases, breast cancer researcher Daniel Hayes of the University of Michigan, Ann Arbor tells Science he is impressed with the work. The team “did all the right things,” says Hayes, who was not involved in the project. Yet, he agrees with Lichtenfeld that the test is not ready to be marketed and sold to clinicians.

There’s more work to be done to improve the test, but the results show it is “additive and complementary” to standard screening, study coauthor Nickolas Papadopoulos of Johns Hopkins University, where the liquid biopsy was developed, tells Science.

A startup called Thrive plans to continue to develop the test for clinical use. But there are uncertainties about how much pre-clinical testing of the test itself will be needed before physicians and oncologists could start using it to search for early signs of cancer, according to Science. Will spotting undetectable cancers be enough or will the test have to show it saves lives? “That is what everybody in the field is grappling with now,” Papadopoulos says.