Tough question! I can only speak from the experiences of my dad from 20 years ago. Key players at that time were Macmillan nurses, the local oncology ward (where my dad finally died) and of course my lovely Mother who did the brunt of the caring . His GP was a waste of space but the other agencies were great but all of it needed a lot of work to stop him falling through cracks.
Keeping in touch with the ward, Macmillan and a local Hospice are key to minimising suffering and maximising enjoyable life.
My dad was lucky to have stayed at home and working on his various projects right up until a few days before he died. He was able to do this through regular blood transfusions and effective pain relief. What eventually "finished him off" was a spinal compression that left him paralysed, but he did not suffer I can say this with certainty because we had a system of hand squeezes agreed so even when he was semi conscious I could be sure he wasn't suffering. I am convinced that the morphine syringe driver actually killed him because he died just after it activated but I knew he was ready to go so it was a relief all round but I still mis him and his thoughtful insite on life....