If you haven’t seen this already you might wanna check out this article https://www.sciencedaily.com/releases/2020/05/200512151941.h...
Good luck and hope your friend can recover fast!
A friend of mine, who was diagnosed with prostate cancer, went through a radical change of diet. This included juicing lots of vegetables and cutting out most meats.
He thinks the dietary adjustment played an important role in his cancer disappearing five years ago.