Scientists believe they have discovered a way to "steer" the immune system to kill cancers.
Researchers at University College, London have developed a way of finding unique markings within a tumour - its "Achilles heel" - allowing the body to target the disease.
But the personalised method, reported in Science journal, would be expensive and has not yet been tried in patients.
Experts said the idea made sense but could be more complicated in reality.
However, the researchers, whose work was funded by Cancer Research UK, believe their discovery could form the backbone of new treatments and hope to test it in patients within two years.
They believe by analysing the DNA, they'll be able to develop bespoke treatment.
People have tried to steer the immune system to kill tumours before, but cancer vaccines have largely flopped.
One explanation is that they are training the body's own defences to go after the wrong target.
The problem is cancers are not made up of identical cells - they are a heavily mutated, genetic mess and samples at different sites within a tumour can look and behave very differently.