I don’t really work on finding a cure for cancer. I try to find out what causes cancer so that we can try to stop people getting it in the first place. I also work on cancer screening so that we can try to diagnose cancer early or even catch pre-cancers before they turn into cancers.
There almost certainly won’t ever be a single cure for cancer, because cancer isn’t really just one disease: each type of cancer is different, and even if two people have the same type of cancer it will be at least slightly different in each person. So each individual cancer will respond differently to different drugs.
That means that we have an awful lot of diseases to find cures for!
Cancer is an enormously complex range of over 200 diseases – and so a ‘cure for cancer’ doesn’t really make sense. Our limits of understanding are hard to define though – it would be easy to blame it on money, or lack of people. I suppose that underdeveloped technology could also be a limiting factor – although our ability to rapidly sequence DNA has been of great help to cancer research.
I think though, that the complexity of the problem is the main thing preventing progress. It’s a great question, and one which research institutes must ask themselves regularly – and attempt to answer!