Blood test could detect many types of solid cancer

A cancer blood test that detects one molecule of tumor DNA among 10,000 healthy DNA molecules in the blood is promising, Stanford University School of Medicine researchers say. Dr. Maximilian Diehn and Dr. Ash Alizadeh of Stanford University School of Medicine and postdoctoral scholars Aaron Newman and Dr. Scott Bratman, and colleagues said previous versions of cancer blood tests also monitored levels of tumor DNA circulating in the blood, but they needed too much time and were not that sensitive. "We set out to develop a method that overcomes two major hurdles in the circulating tumor DNA field," Diehn said in a statement. "First, the technique needs to be very sensitive to detect the very small amounts of tumor DNA present in the blood. Second, to be clinically useful it's necessary to have a test that works off the shelf for the majority of patients with a given cancer." The findings were published in Nature Medicine. The Stanford University School of Medicine approach -- Cancer Personalized Profiling by deep Sequencing, known as CAPP-Seq, is highly sensitive, specific and timely -- it accurately identified about 50 percent of people in the study with stage-1 lung cancer and all patients whose cancers were more advanced. Cancer cells are always dividing and dying, but as they die, they release DNA into the bloodstream revealing genetic messages but learning to read the messages on the tumor, mutations and patient therapy response is difficult. "The vast majority of circulating DNA is from normal, non-cancerous cells, even in patients with advanced cancer," Bratman said. "We needed a comprehensive strategy for isolating the circulating DNA from blood and detecting the rare, cancer-associated mutations. To boost the sensitivity of the technique, we optimized methods for extracting, processing and analyzing the DNA."