A blood test that can detect several types of cancer before a person falls ill has been hailed as a 鈥渉oly grail鈥� by many newspapers, but to be useful it will need to be refined to become much more accurate, otherwise it could fail to detect large numbers of cancer cases.
In a study of 749 people without cancer, and 878 people who had been newly diagnosed with cancer, the test detected 90 per cent of cases of ovarian cancer, and 80 per cent of cases of pancreatic, liver and gallbladder cancers.
It fared worse at other cancers, detecting 77 per cent of lymphoma cases, 73 per cent of myeloma cases and 66 per cent of bowel cancer cases.
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鈥淢ost cancers are detected at a late stage, but this 鈥榣iquid biopsy鈥� gives us the opportunity to find them months or years before someone would develop symptoms and be diagnosed,鈥� Eric Klein, from the Cleveland Clinic in Ohio, . 鈥淭his is potentially the holy grail of cancer research, to find cancers that are currently hard to cure at an earlier stage when they are easier to cure, and we hope this test could save many lives.鈥�
The findings will be presented at the American Society of Clinical Oncology annual meeting in Chicago this weekend.
False negatives
But such a test would need to be much more accurate to be useful for cancer screening. For example, a 90 per cent accuracy rate 鈥� as seen for ovarian cancer 鈥� would still mean a large number of incorrect diagnoses.
In the UK, around 7000 women get ovarian cancer for every 100,000 in the population, so a 90 per cent accuracy rate would see 700 of these women incorrectly given the all clear 鈥� a false negative.
Conversely, mass screening for cancers can also lead to large numbers of false positives, leading to unnecessary, invasive treatments for people who are at low or no risk.
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