To the people who say alternative therapies are bogus, well that's a poor argument. I have access to thousands of peer reviewed studies that prove the opposite.
http://www.ncbi.nlm.nih.gov/sites/entrez/ Look for studies here.
Supplement wise, high dose vitamin d3(or a lot of sunlight), and if hes doing chemotherapy, Theanine. If I had cancer this is what I would do.
"There are also more than a dozen reports in the scientific literature which show a clear benefit of theanine in fighting various forms of experimental cancer. In many of these studies, theanine has been shown to enhance the anti-tumor activity of some cancer drugs such as pirarubicin, doxorubicin and adriamycin. It appears that theanine slows the ability of the tumor cells to eject the cancer drugs - so combination therapy with the chemotherapy agent plus theanine seems to maintain high levels of the drug in the tumor cells and both slow their growth and accelerate their death."
I would probably start consuming green tea and other antioxidant/anticancer foods by the handful.
If he's depressed or has anxiety, which is common for people with terminal diseases, something like rhodiola rosea, ashwagandha, lithium orotate, and/or high dose Taurine would be good.
If there is a will, there is a way. Don't give up, ever.