Hope for early detection: New cancer blood test may find 8 kinds of tumours
Cancers were detected in the ovaries, liver, stomach, pancreas, esophagus, colorectal, lung and breast. For five of these cancer types -- ovary, liver, stomach, pancreas and esophagus -- there are no screening tests available for people of average risk.fitness Updated: Jan 19, 2018 22:10 IST
Scientists at Johns Hopkins University in the US have taken the first step towards a universal blood test for cancer by conducting trials of a non-invasive test that detects eight common types of the disease long before any symptoms arise.
The test called CancerSEEK, first reported in Science journal, detected cancers of the ovary, liver, stomach, pancreas, esophagus, colo-rectum, lung and breast when it was applied to 1,005 patients who had already been diagnosed with the disease.
“CancerSEEK tests were positive in a median of 70% of the eight cancer types. The sensitivities ranged from 69% to 98% for the detection of five cancer types (ovary, liver, stomach, pancreas, and esophagus) for which there are no screening tests available for average-risk individuals,” Science reported.
The test was also able to localise the cancer to a small number of anatomic sites in 83% of the patients, the report said.
Scientists are excited about the first non-invasive blood test that can simultaneously screen for a range of cancers but the researchers believe further studies are needed before CancerSEEK can be made widely available for its projected cost of less than $500.
CancerSEEK focuses on detecting mutations in 16 genes that are linked to cancer and eight proteins that are often released by tumours into the bloodstream. Increasing the number of mutations and proteins analysed will allow CancerSEEK to look for a wider range of cancers.
“The ultimate goal of CancerSEEK is to detect cancer even earlier – before the disease is symptomatic,” said the report.
The researchers at Johns Hopkins have a vision for an annual test designed to catch cancer early and save lives, BBC reported.
Cristian Tomasetti from Johns Hopkins University School of Medicine told the BBC: “This field of early detection is critical. I think this can have an enormous impact on cancer mortality.”
Finding tumours so that they could be surgically removed would be “a night and day difference” for survival, said Tomasetti.
Outside experts said more research is needed to uncover the true accuracy of the test and whether it will be able to detect cancers before they cause symptoms.
CancerSEEK is now being tried on people who have not yet been diagnosed with cancer, which will be the real test of its usefulness. Researchers are hoping it can complement screening tools such as mammograms for breast cancer and colonoscopies for colorectal cancer.
“This looks promising but with several caveats, and a significant amount of further research is needed before we can even contemplate how this might play out in screening settings,” said Mangesh Thorat, deputy director of the Barts Clinical Trials Unit at Queen Mary University of London.
“The sensitivity of the test in stage I cancer is quite low, about 40%, and even with stage I and II combined it appears to be around 60%. So the test will still miss a large proportion of cancers at the stage where we want to diagnose them.”
Nicholas Turner, professor of molecular oncology at The Institute of Cancer Research, London, pointed out the test’s 1% false positive rate may sound low but “could be quite a concern for population screening. There could be a lot of people who are told they have cancer, who may not have it.”
However, Turner described the development as “a step along the way to a possible blood test to screen for cancer, and the data presented is convincing from a technical perspective on the blood test”.
Many other efforts are under way to develop blood tests for cancer. “I do not think that this new test has really moved the field of early detection very far forward,” said Paul Pharoah, professor of cancer epidemiology at the University of Cambridge. “It remains a promising, but yet to be proven technology.”
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First Published: Jan 19, 2018 10:06 IST