I'm very sorry to hear about your uncle.
Unfortunately many people are not organ donors and even if they were there are problems of compatibility and logistics (i.e. how you transport those organs in time). Regenerative medicine is a growing field and there have been many breakthroughs in recent years with simple tissues like those found in the trachea but we are a long way from growing whole, viable organs.
Sometimes it is a problem of identifying the tumour, other times the problem is that by removing the tumour you irrecoverably damage the organ and thus it will die anyway. A bigger problem though is that whilst tumours are macroscopic there can still be microscopic cancer cells left behind and (in the case of metastatic cancers) in the process of migrating through the body. Some of these cells can latch on to tissues and begin growing organs again.
We have come a long way in cancer therapies over the last few decades but it is still an incredibly complex and difficult to treat condition. There are constant improvements to therapies but unfortunately we will not get to the stage where suddenly all cancers are trivial to treat. More likely we will make incremental, slow but steady progress (at different rates for different cancers) until eventually we look back and realise how different things were at a great remove.