In popular mythology, cancer has to be “caught early” before it has a chance to spread. The biological reality is quite different: by the time a tumour becomes detectable, spread has, in many cases, already occurred. “A high proportion of early cancers have already thrown off occult metastases by the time the primary tumour is diagnosed,” the British oncologist Basil Stoll has pointed out.17 However, most metastases either die or lie dormant for a long time