End stage lung cancer/high calcium levels?

My father-in-law was diagnosed with small cell lung cancer three years ago, he has done both chemo and radiation treatments. The cancer spread to his brain. Both the tumors in his lungs and brain have shrunk, but they are still present. He was hospitalized last week because he has been very disoriented, and incontinent. They ran some tests and said his calcium was very high and that this caused by the end stage of cancer. He has been hospitalized again this week, but now the dr. is saying his calcium is still high, but not high enough to cause his symptoms. They are saying now that he is just having seizures. Here are my questions. Does cancer have to be very large to be considered at the end stage? Remember I said that his has shrunk. And what could be causing him to be completely confused and disoriented? His blood pressure gets really high when this starts happening as well. These symptoms come and go, he will be fine one second and the next be talking very strange. They said there was no sign of stroke.