Researchers developed a single blood test, CancerSEEK, that screens for eight common cancer types and helps identify the location of cancer. The test is a unique non-invasive, multianalyte test that simultaneously evaluates levels of eight cancer proteins and the presence of cancer gene mutations from circulating DNA in the blood. The study findings published in Science.
Circulating tumour DNA mutations can be highly specific markers for cancer. The team sought to develop a small yet robust panel that could detect at least one mutation in the vast majority of cancers. In fact, keeping the mutation panel small is essential to minimize false-positive results and keep such screening tests affordable.
The molecular test is aimed at cancer screening and, therefore, is different from other molecular tests, which rely on analyzing large numbers of cancer-driving genes to identify therapeutically actionable targets. In the study, the test had greater than 99% specificity for cancer.
The test was evaluated patients with nonmetastatic, stages I to III cancers of the ovary, liver, stomach, pancreas, oesophagus, colorectum, lung or breast. The median overall sensitivity, or the ability to find cancer, was 70%. The method combines the probability of observing various DNA mutations together with the levels of several proteins.
Another new aspect of the approach is that it uses machine learning to enable the test to accurately determine the location of a tumour down to a small number of anatomic sites in 83% of patients. Although the current test does not pick up every cancer, it identifies many cancers that would likely otherwise go undetected.
To zero in on the analytes they included in their CancerSEEK test, the research team pulled data from more than three decades of cancer genetics research generated. To precisely determine the optimal number of DNA bases to assess in the CancerSEEK test, the researchers used a method based on diminishing returns.
The more DNA bases you assay, the more mutations you are capable of finding, but eventually, you reach a point of diminishing returns. The present test designed to reflect this point of diminishing returns, including the DNA markers that were useful for detecting the cancers and eliminating those that did not add benefit.
CancerSEEK is noninvasive has the potential to substantially impact patients. Earlier detection provides many ways to improve outcomes for patients. Optimally, cancers would be detected early enough that they could be cured by surgery alone, but even cancers that are not curable by surgery alone will respond better to systemic therapies when there is less advanced disease. The test represents the next step in changing the focus of cancer research from late-stage disease to early disease, which will be critical to reducing cancer deaths in the long term.