Longevity Briefs: A Blood Test To Detect 50 Types of Cancer

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: Early detection of cancers can be extremely important for the survival outlook of the patient. Certain cancers such as pancreatic cancer are very hard to detect in their early stages, making them more deadly as treatment may not begin until the cancer has already spread throughout the body. Developing tests to screen for cancers in those most at risk may save many lives. For such a test to be useful in screening a large number of individuals, it must be sufficiently specific (have a low false positive rate).

What did the researchers do: Researchers previously developed a blood test for cancer that uses machine learning to analyse cell-free DNA (cfDNA), which is shed by normal cells and cancer cells. Genomic sequencing is used to detect methylation – a chemical change in which ‘tags’ are added to the DNA and that can control gene expression. The machine learning algorithm is used to detect methylation patterns that suggest that cancer is present, and also predicts where the cancer is likely to be located. In this study, researchers studied the test’s ability to detect cancer in 4077 participants who were either diagnosed with cancer and/or were scheduled to undergo biopsy for a suspected cancer.

Key takeaway(s) from this research: The test was able to detect more than 50 different types of cancer. Across all cancer stages (I, II, III, IV), the test picked up 51.5% cancers (sensitivity). The test’s ability to avoid false positives (specificity) was 99.5%, meaning that the test wrongly detected cancer in only 0.5% of cases. In practice, this means that a positive test result has a 44.4% chance of being correct in those most likely to develop cancer, while a negative result has a 99.4% chance of being correct. If you’re confused as to why these numbers are different, you might be interested in reading this article. The test correctly identified the location of the cancer in 88.7% of cases. Previous results suggest that the test is capable of detecting cancers before symptoms emerge.

The test is sufficiently sensitive and specific that it could be rolled out as a screening test in those who are at higher risk of cancer including those over 50 years of age. The test is being piloted by NHS England in the autumn.

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