Today.Az » Weird / Interesting » Cancer 'can go undetected for a decade'
18 November 2011 [13:00] - Today.Az


Millions of people carry tumours which go undetected for a decade because they do not shed tell-tale substances into bloodstream, a study claims.

Currently available blood tests help doctors identify cancer by the presence of substances which are produced by tumours and seep into the bloodstream.

But a mathematical study by Stanford University scientists in America indicates that it could take a cancer cell a decade or even longer to grow into a tumour and begin secreting enough of these so-called biomarkers to be picked up in a screening.

Many biomarkers made by tumour cells are also produced naturally in a healthy body, so it can take years before they reach a high enough concentration to cause concern.

More sensitive tests are needed and more distinctive biomarkers must be found in order to bring about earlier diagnoses of cancer, which are key to the success of any treatment, researchers said.

The study, the first to connect the size of a tumour with the level of biomarkers it releases into the bloodstream, found that an ovarian tumour would have to reach the size of 1.7 billion cells before the best available test could detect it.

It would be the size of a 2cm cube and would have been present in the body for between 10 and 13 years before high levels of its most distinctive biomarker became unusually high, they said.

In theory, a similar biomarker which was not produced elsewhere in the body could be detected within eight years, when the tumour would be the size of a four millimetre cube.

Prof Sanjiv Gambhir, who led the study, said: "It’s really important for us to find biomarkers that are made exclusively by tumour cells.

"The good news is that we have potentially 10 or even 20 years to find the tumour before it reaches this size, if only we can improve our blood-based methods of detecting tumours."

Early detection is seen as the key to beating most types of cancer, with 90 per cent of ovarian cancer patients surviving if their tumour is detected at an early stage.

But more than 80 per cent of patients are not diagnosed until the late stages of the disease, by which point their chances of living for another five years are less than three in ten.

The researchers built their model, described in the Science Translational Medicine journal, by calculating how fast particular tumours grow from a single cell, how much of a particular biomarker they release each hour and how much biomarker they must have produced for it to stand out from normal levels in current tests.

Two years ago, a study by a separate team at Stanford found that existing tests for ovarian cancer were unable to detect tumours early enough to significantly alter the mortality rate.

Dr Laura McCallum, of Cancer Research UK, said: “Detecting cancer at an early stage when treatment is more likely to be successful is one of the most promising ways to reduce deaths from the disease.

"Biomarkers have the potential to offer a simple, non-invasive way to detect cancer early and scientists, including our own, are working hard to find ones that can do this reliably.

"Mathematical models like this, designed to predict the most effective biomarkers, could help improve the bench to bedside success of such tests in the future.”


/The Telegraph/
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