Cancer paintings

In starting out with this new series of paintings I've become more aware of the number of people closely connected to me who have either beeen diagnosed and treated with various forms of cancer or are at a stage where there is little more that can be done for them. In a good number of cases the people concerned have died as a result of cancer.
It is something that affects people of all ages all over the world. I am at present doing a painting of my brother who is in stage 4 of brain cancer. As I look at photos of him and remember many occasions in his life it brings on great feelings of sadness and loss. It is strange to think that as I wake up every morning looking forward to a new day and the challenges and opportunities that it brings, it must be a huge challenge for him to deal with a sense of a fast ebbing tide. While he is glad to greet each new day he knows that his time is limited. He has been valiant in dealing with it up to now, always keeping the sunny side out and never wanting to make a fuss or put people to trouble. It is hard to see the changes and the gradual deterioration in his condition.
How can I do a painting of him that does not offend or lack sensitivity to his terminal condition? Even using the words 'terminal condition' seem to sound harsh and blunt. How do you capture a person's character and yet show the effects of terminal cancer?