EXCLUSIVE How cancer doctors try to keep themselves free of cancer: Eight experts reveal their science-backed habits in our definitive guide on how to protect yourself By JUDITH KEELING Published: 19:49 EST, 22 February 2025 | Updated: 19:49 EST, 22 February 2025 e-mail View comments Why does one person develop cancer and another does not? For some people, it's sheer bad luck, caused by genes they've inherited, for example, or random chance mutations in the body's renewal processes – not an unlikely scenario, given that some 330 billion cells are repaired and replaced on a daily basis. But increasingly, scientists believe that the way we live – what we eat and drink, our exercise levels, whether we smoke or if we are exposed to environmental pollutants – plays a major role. Last year, a US study that looked at lifestyle habits of two million people over 20 years concluded that around 45 per cent of cancers might be caused by lifestyle and were entirely preventable.
'We now know that cancer starts developing a long time before symptoms show or signs can be detected on blood tests, for example,' says Sarah Blagden, a professor of medical oncology at the University of Oxford . 'For bowel cancer, it's 20 to 30 years beforehand – and, for many others, including pancreatic and lung cancers, it can be decades,' she adds. 'Regardless of the type of cancer, the process by which the disease develops – from the first genetic mutation in a cell into a tumour – is a long one a.