Yes Riv, those are nice words there. Jack, I have been thru the cancer recovery process. River is right about consulting with the wife on when would be the best time to stop by. Don't be afraid to ask him how he is? He will let you know, men especially need to talk about it. In a strange way, it helps make sense of it all.
I will say this... It's much better on your conscious and your friends conscious to face the awkwardness, than to not stop and see him at all. It's a little uncomfortable right at first, but then conversation just picks up and the two of you will talk and chuckle, maybe even have a good laugh. When you leave his house and get into you car and drive away, you will be left with a wonderful warm spot in your heart that you did the right thing.
Personally, I didn't mind talking to my friends about what I was going thru, it actually helped relieve built up fear and tension.
Here's another real nice thing you can do. Ask his wife if you can bring a casserole or dinner for him and her (or the family). Ask what it is that he can eat. A large pot of homemake chicken noodle soup is alway a hit with cancer patients. It's easy on their traumatized stomach, and it's comforting to eat, and smells delicious. It was a great help in my household because hubby didn't know how to cook much. Taking care of your friend and the one taking care of him is important.