"Researchers say they have taken a big step towards developing a test that can tell people if they have cancer long before the first symptoms show up. The blood test detected the majority of cancers in people with four of the biggest cancer killers breast colon lung and ovarian cancer the team at Johns Hopkins University said. The test is a long way from being used to screen for cancer but the study shows a way to get there the team reported in the journal Science Translational Medicine. There is a lot of excitement about liquid biopsies but most of that has been in latestage cancer or in individuals where you already know what to look for said Dr. Victor Velculescu professor of oncology and pathology at the Johns Hopkins University Kimmel Cancer Center. The surprising result is that we can find a high fraction of earlystage patients having alterations in their blood said Velculescu who led the study team.  It was not a slam dunk but the test found cancer in the blood of more than half the patients who had been diagnosed with stage  cancer. It was even more accurate in finding latestage cancers but the goal would be to catch cancer in its earliest easiesttotreat stage. There were no false positives in  people who did not have cancer they said. Thats important said Dr. Wyndham Wilson of the National Cancer Institute because there is no point detecting cancer in people if the cancer is not going to actually cause trouble. You dont want to go screening people for hallmark cancer mutations unless you absolutely know that when you find it that there is a tumor there and that it is a tumor that needs to be treated said Wyndham who was not involved in the study. Sometimes earlystage tumors or precancerous growths just go away  attacked by the immune system or because they dont thrive for other reasons. Several different liquid biopsies are already on the market used to help track whether cancer treatments are working. But theres nothing yet that can detect cancer in someone who has not yet been diagnosed. Its easy to find tumor mutations if you know what to look for. The challenge was to develop a blood test that could predict the probable presence of cancer without knowing the genetic mutations present in a persons tumor Velculescu said. Velculescus team developed an approach called targeted error correction sequencing TECSeq for short. We have used this approach to examine  cancerrelated genes the team wrote in their report. The method involved deep sequencing  sequencing DNA  times over to look for mutations in DNA from tumor cells that floats in the blood. Cancer patients had more of this DNA in their blood the team found. They identified  percent of the patients with stage I cancer  four out of eight colon cancer patients and  percent of colon cancer patients with stage II III or IV disease. They got a positive in  percent of the lung cancer patients with stage I disease  percent of ovarian cancer patients with stage I disease and  percent of breast cancer patients with stage I disease. While thats good its not a great result. The test still missed a large percentage of cancers and will need much improvement Velculescu said. It will also have to be tried in larger groups of patients and patients with different cancers. The first goal would be to try it in people at high risk of cancer but no symptoms yet  such as smokers or people with cancercausing gene mutations like BRCA mutations Velculescu said. Wyndham said it will be important to study such tests in large groups of people who have not had cancer diagnosed to see if it can truly be used to screen asymptomatic people for cancer. And then it will have to be shown that using the test allows doctors to intervene sooner and help people. Catching cancer in its earliest stages could save many lives. Cancer is the No.  killer overall in the United States. The survival difference between late stage and early stage disease in these cancers would account for more than a million lives each year worldwide Velculescu said. The genetic sequencing is also expensive right now  on the order of several thousand dollars for the  repeats the team did. But costs are coming down steadily he said. Velculescu said Johns Hopkins had patented this test and Velculescu is himself the founder of a company that does liquid biopsies for advanced cancer patients called Personal Genome Diagnostics. The U.S. Food and Drug Administration has been very skeptical  http blood tests that claim to diagnose disease  http people have symptoms. The agency has chastised a company called Pathway Genomics http over its liquid biopsy test http  saying the company had not shown the  test worked as advertised. Its also warned other gene testing companies  http finally gave andMe the goahead http to market its home DNA test  which does not include any cancer screening  in April. Cancer screening is still often a tricky issue. Currently colon cancer can be detected very early with colonoscopies http and even stopped before precancerous growths get out of control. But colonoscopies are uncomfortable and carry a small risk of injury. Mammograms can detect early breast cancer http Pap smears can detect cervical cancer http or precancerous changes and a type of specialized chest xray called a spiral CT  http detect lung cancer. Theres a debate over the usefulness of screening for prostate cancer http but blood tests and physical exams can indicate some men at high risk"