In a global first, a blood test that can detect 50 different types of cancer with 99% accuracy is now a part of a large, national health trial. Known as the Galleri test, the rapid cancer diagnostic will be available to more than 160,000 patients of England’s National Health Service by mid-2021.
While scientists have created blood tests for cancer screening previously, this test is the most accurate, correctly diagnosing 99% of 1,200 cancer patients involved in an earlier trial. The test also correctly identified tissue in which the cancer originated in 93% of cases. This unprecedented level of accuracy has prompted the NHS to roll it out on a larger scale, in hopes it will aid the early diagnosis of cancer cases.
“While the good news is that cancer survival is now at a record high, over a thousand people every day are newly diagnosed with cancer. Early detection — particularly for hard-to-treat conditions like ovarian and pancreatic cancer — has the potential to save many lives,” Sir Simon Stevens, NHS England’s chief executive, said according to The Independent.
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However, the test’s effectiveness at early-stage cancer diagnosis is spotty. Research published in the journal Annals of Oncology in March 2020 found the test detected cancer correctly in only 18% of stage 1 cancer cases, versus 43% of cases in stage 2, 81% of cases in stage 3, and 93% of cases in stage 4.
That’s why some experts are advising caution about widespread adoption of the Galleri test. “Based on the evidence we have seen, the test is not currently that good at picking up stage I cancer, where it is small and hasn’t spread to other parts of the body,” Dr. Jodie Moffat, head of early diagnosis at Cancer Research UK, told the Science Media Center. She adds, “… Sample sizes, particularly for some cancer types, have been very small and so it needs to be tested in a much larger sample, and with longer follow up of patients not testing positive with the blood test to understand where it is missing cancers.”
