Currently available blood tests help identify cancers by the presence of substances they secrete into the bloodstream. But, the new study led by Prof Sanjiv Gambhir of Stanford University in the US showed that it could take a cancer cell a decade or even longer to grow into a tumour and begin shedding enough of these 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, the Daily Telegraph reported.

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

'It's really important for us to find biomarkers that are made exclusively by tumour cells, said Prof Gambhir.

'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.'