A new blood test in development may offer new hope in the early detection of cancer. The test has demonstrated the ability to detect numerous types of cancer with a high degree of accuracy. Researchers from Dana Farber Cancer Institute presented the results of the multicenter new study at a session of the European Society for Medical Oncology Congress, ESMO 2019.
The test, developed by GRAIL, Inc., uses a new sequencing technology called “Next Generation Sequencing” or NGS. This examines DNA for tiny chemical marks (methylation) that influence whether genes are active or inactive. When applied to nearly 3,600 blood samples - some from cancer patients, others from people who had not been diagnosed with any disease at the time the blood was drawn - a cancer signal was successfully detected from the samples. The test correctly identified the tissue from which the disease originated. So the specificity of the blood test is its ability to give a positive result only when cancer is actually present. The results also showed the option of locating the organ or tissue of origin, researchers found.
The new test looks for DNA that cancer cells release into the bloodstream when they die. Unlike biopsies, which detect genetic mutations or other cancer-related changes in DNA, the technology focuses on modifications known as methyl groups. Methyl groups are chemical entities that can bind to DNA in a process called methylation. This allows you to controlwhich genesactive and which are inactive. In many cases, abnormal methylation patterns are more likely to indicate cancer than mutations. The new test looks at parts of the genome where abnormal methylation patterns are found in cancer cells.
Research results with new perspectives
“Our previous work has shown that methylation-based assays outperform traditional DNA sequencing approaches for detecting multiple cancers in blood samples,” said study lead author Dr. Geoffrey Oxnard. “The results of the new study show that such tests are a viable way to screen people for cancer.”
In the study, the researchers first analyzed cell-free DNA. This was once limited to cells, but entered the bloodstream after cell death. The test was carried out in 3,583 blood samples, including 1,530 from cancer patients and 2,053 from healthy people. Patient samples included more than 20 cancer types, including breast, colon, esophageal, gallbladder, stomach, head and neck, lung, lymphoid leukemia, multiple myeloma, ovarian and pancreatic cancers.
The overall specificity was 99.4%, meaning that only 0.6% of results incorrectly indicated the presence of the disease. Sensitivity of the test for detecting a given cancer with high mortality (the percentage of blood samples from these patients that tested positive) was 76%. Within this group, sensitivity was 32% in stage I patients; 76% for those with stage II; 85% for Stage III; and 93% for stage IV. Sensitivity across all cancer types was 55%, with detection increasing similarly by stage. For the 97% of samples that yielded a tissue of origin, the test correctly identified the organ or tissue of origin 89% of the time.
Detecting a modest percentage of common cancers early could translate into many patients potentially receiving more effective treatment if the test were widely available, Oxnard noted. You can find the link to the studyhere.
