In a 66-year-old woman like Maggie, a stone of weight loss over a couple of months, accompanied by nausea, right-sided chest pain and indigestion, represents cancer until proven otherwise. The problem was: where? The clinical examination was unremarkable. A battery of blood and urine tests failed to provide any clue, as did a chest X-ray. A stool sample to detect a bowel tumour came back resoundingly negative. Gastroscopy, where a camera on a fibre-optic cable allows direct inspection of the stomach, also drew a blank. Cancers of the pancreas or ovary are notoriously difficult to identify; an urgent CT scan of her chest, abdomen and pelvis proved clear.
All of this took many weeks to perform and was still ongoing last month when the impending Galleri trial was in the news. Galleri is a test that aims to detect minute traces of genetic material that leaks from tumours into the bloodstream. Preliminary studies suggest it is able to identify more than 50 different cancer types and to correctly predict the organ of origin 90 per cent of the time. It has been developed by a California-based biotechnology firm, Grail. The name is well-chosen: a single blood test that could pinpoint the cause in a case such as Maggie’s is a holy grail indeed.
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