How long can cancers grow before detection?

Kat - Absolutely not at all. Then screening wouldn't work. Things like the breast screening and the bowel screening that we have now. Some cancers, yes, they are advanced and that's why the government's trying to do a lot through an initiative called the early detection and awareness initiative to try and catch cancers earlier. Bowel cancers you can spot them when they're just a little polyp. You can take them away and cancer will not have grown anywhere. In the case of breast cancers, breast screening picks up very small tumours that really haven't spread far so it's not necessarily true for all types of cancers that they will have spread around the place. Chris - Could she mean that cancer's a multistage process where you slowly build up and acquire changes of your DNA which eventually mean you get cancer and you could have spent a lifetime building up those changes? Kat - That's kind of true because we do pick up all kinds of damage to our DNA just in the hurly burly of life within our cells. Cancer is a disease that usually takes a very long time to happen. There is also and idea that we do, everyone has tiny cancers all over us but it's our immune system that's constantly patrolling our bodies and keeping these under control. What happens when cancer really starts to grow is that it started to evade this immune suppression and really start going for it. There's a lot we don't understand about how cancer really gets going.