The exact mechanisms involved are still mysterious, but the likelihood that many cancers are initiated at the level of genes suggests that we will never prevent all cancers.
For the moment, I can't give you any clear answer that this is worth doing because we have to wait for the next two or three years until these nicotinic acid trials are finished.
When initial repairs are inadequate, therefore, it is not because the mechanics lack competence; rather, there is clearly a level of focused concentration that complex repairs require.