One in two people in the UK will be diagnosed with cancer at some point in their lives, analysis suggests.
Cancer Research UK said this estimate, using a new calculation method, replaced a forecast of more than one in three people developing the disease.
It said longer life expectancies meant more people would be affected.
But it was not inevitable and improving lifestyle, such as losing weight and quitting smoking, could have a major impact, the charity added.
The good news is cancer survival figures are also rising.
The seemingly sudden jump in diagnosis estimates is down to researchers developing a more sophisticated and accurate method for analysing the risk of cancer.
However, both the new and old methods show the same long-term trend - a rise in the lifetime risk of developing cancer.
Nearly 54% of men will develop cancer, compared with just under 48% of women, the figures indicate.