Except that early stage intervention tends to mean that less invasive techniques can be used. Removing a small cancerous lump might only require keyhole surgery

Except that early stage intervention tends to mean that less invasive techniques can be used. Removing a small cancerous lump might only require keyhole surgery, while in later stages it might require significantly more invasive surgery. Sure, all surgery carries some risk (much of which, I believe, comes from having to use anesthetics rather than the surgery per-se) but the less invasive it is, the faster the patient can recover from it. Similarly, early stage cancers might call for far less agressive chemotherapy drugs with reduced side-effects and requiring fewer doses. Still, the question of early detection is an interesting one, as is the question of when intervention is necessary. Your comments about the stress of knowing that you might have cancer is interesting in light of a paper which my father published a few years ago about whether to restart treatment with people who had relapsed ovarian cancer when their tumour marker levels started rising again, or when they started to exhibit symptoms. As it turned out, while treating people once their tumour markers crossed a 'red line' meant that intervention started earlier, waiting for symptoms to be exhibited resulted in nearly identical life expectancy and also a higher quality of life as they'd spent less time on chemo. Consequently, it also raised the question of whether or not it's worth regularly checking tumour marker levels after their first cancer had gone into remission, as having to have blood tests every three months and waiting for results each time is stressful in itself.