Hrissy:
I'm very dismayed to learn of your friends gastroenterological cancer. There are excellent cancer centers worldwide and of course, many here in the U.S. The New York-Presbyterian Cancer Center is a place I would contact if I was diagnosed with cancer. The Cancer Treatment Centers of America are another excellent facility and, as their name implies, specialize in cancer treatment. Memorial Sloan-Kettering Cancer Center in New York City is highly-rated for cancer treatment, as is the Dana-Farber Cancer Institute in Boston, Massachusetts. Johns Hopkins Hospital located in Baltimore, Maryland is well-respected as is the famous Mayo Clinic i in Rochester, Minnesota. These are just a few in the U.S.
I would use the internet to search these institutions and others, worldwide, to find out more, as well as how to contact them, individually.
I trust this is of at least a little benefit to you, Hrissy, and that your friend can be helped. Know that he is my prayers.
Jim