Just been an absolute blessing. a deep breath in, sharp scratch. so how can a blood test tell if a patient like ben is free of cancer? it looks for tiny fragments of tumour dna circulating in the bloodstream. if there's none present, there is a low risk the cancer will return. these blood tests, or liquid biopsies, are part of a revolution in the diagnosis and monitoring of cancer. they're being trialled in the uk across lung, breast as well as bowel cancer, and can detect minute fragments of tumour dna months, even years before it would show up on a scan. ben has regular checkups at the royal...