It is likely that one day a single blood test can be used to detect a variety of cancers. In the last few years a variety of tests called liquid biopsies have been developed that hold the hope of detecting and tracking tumors from a simple blood draw. Many of the tests detect tumor-associated DNA mutations. But detecting scant DNA released by early stage tumors is daunting. Furthermore, false positives are a constant concern. In an online post in the journal Science (Cohen et al , Science), researchers and collaborators at Johns Hopkins reported on a newly developed test dubbed CancerSEEK. The test examined the levels of 8 tumor-related proteins and the presence of mutations in 16 genes often mutated in various cancers. The researchers tested this liquid biopsy on 1005 patients diagnosed with non-metastatic cancers of the ovary, liver, stomach, pancreas, esophagus, colo-rectum, lung and breast. The accuracy of CancerSEEK varied depending on the cancer: it detected 98% of ovarian cancers but only 33% of breast cancers. However, in looking at the entire cohort, the sensitivity was 69% or higher for cancers of the ovary, liver, stomach, pancreas and esophagus. The false positive rate in 812 healthy patients was <1%. One caveat is that the cancer-related proteins can also appear in people with inflammatory diseases such as arthritis and may increase the false positive rate in this population.
A study of CancerSEEK is now underway in the Geisinger Health System in Pennsylvania on female volunteers between ages of 65 and 75 who have never had cancer. The study is being done in collaboration with Johns Hopkins. For those patients who test positive twice, imaging will be used to attempt to find a primary tumor.
“If people expect to suddenly catch all cancers, they’ll be disappointed,” says cancer researcher Nitzan Rosenfeld of the University of Cambridge in the United Kingdom. “This is exciting progress,” he says. “But evaluating it in the real world will be a long process.”