Posted on Oct 09, 2023, 4 p.m.
The test, Galleri®, developed by the firm Grail, searches for fragments of cancerous DNA in the blood, and it is reported in the journal The Lancet, by researchers from New York’s Memorial Sloan Kettering Cancer Center, to detect one cancer case for every 189 over-50s tested.
“The possibility of screening for multiple types of cancer simultaneously using a blood specimen is promising both because there are no effective screening strategies for many types of cancer and because strategies with established effectiveness require considerable time and effort,” noted Deb Schrag, MD, MPH, Chair, Department of Medicine at Memorial Sloan Kettering in New York and a PATHFINDER investigator.
Using a single sample to detect fragments of tumor DNA in the blood that circulate around the body when they break off, the pilot study screened 6,662 people over the age of 50 with no symptoms of cancer. The test provided a positive result to 92 of them, 35 of them were actually diagnosed later, meaning that 57 people were given a false positive, but 35 were diagnosed early before displaying any symptoms.
“This study provides early evidence of the feasibility of blood testing to screen for multiple cancers with a single test,” said the authors. “Importantly, it detected many cancer types for which screening tests do not exist, including some found at early stages.”
Over 375,000 cases of cancer are diagnosed annually in the UK alone, and approximately 167,000 people die from cancer every year. Gaining the ability to detect tumors before patients display symptoms leads to earlier treatment options and boosts the chances of positive outcomes.
However, the blood test will need further refinement before it is used broadly, as telling patients that they have cancer when they don’t can be detrimental to mental health, and the additional follow-up testing to confirm the results would add an extra strain on the healthcare system.
“The exciting data in these studies should not outshine more sobering concerns,” said Dr Richard Lee, a cancer doctor at the Royal Marsden in London, who was not part of the study. “False-positive patients are at high risk of screening harm and psychological effects require consideration.”
Earlier, an Oxford University Trial found the screening successful at detecting cancer in the blood of two-thirds of the people with symptoms. The study involved 5,461 patients, of which the test detected cancer in 244 out of the 368 patients who had cancer. The test was found to be more accurate in those who already experienced pain or had lumps, giving a correct negative result for 98% of those without cancer, saving the need for additional testing.
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