Brother diagnosed with thyroid cancer and thinks he can cure himself with hemp o!

There's this stupid video on youtube about a bunch of people who allegedly cured their cancer with "hemp oil". I tell him he's stupid for being so gullible. He showed me several "Scientific journals" that claim that cancer cells have been killed with THC, the active ingredient in marijuana, in "in vitro" studies. I told him that "in vitro" is different from "in vivo" and that the results in a petri dish don't always translate to flesh and blood. The doctor told him his only chance was getting most of his thyroid removed and undergoing chemotherapy. I told him to trust the experts but he says all they want to do is poison him. We did know a lady who got cancer and got chemotherapy and died in the second round but that doesn't mean that will happen to him. Most people survive chemotherapy. What should I do? How do I convince him? Thank you so much for your help.