Friend starting chemo for testicular cancer soon - How can I best support him? I live too far away to visit and don't want to say the wrong thing

Hello, I'm looking for some advice, but not sure this is the right forum. A close friend of mine has been diagnosed with testicular cancer and is starting chemo very soon. I really want to support him, but don't know how best to do this. We have never really chatted much about our health before, and i live too far away to visit him, so i'm wracking my brains to think of other ways to show I care. I'm really fortunate that neither i nor my close family have had a cancer diagnosis or experienced chemo so I don't actually know what it is like, only from what i have heard or read about. I just don't want to say the wrong thing and in fact maybe not talking about it is best. We normally laugh and joke about things together, but this doesn't feel right either. I want to be useful, but that is hard being so far away but i also don't want to say the wrong thing. Can you offer any advice on how to talk about it or what to say?