Hi.
Your instinct is probably correct. It's likely that your friend feels awkward about the subject of his cancer, too, especially if he's not used to getting into "deep" stuff. He's also probably not the type to want or to expect pity.
On the other hand, you are good friends and it must feel awfully weird for you NOT to talk about such an obvious thing.
Perhaps the best way to proceed is simply to acknowledge how strange the situation is. When you feel there is an opening to talk about his situation, just say, "Hey, this is weird, huh? I never expected to be talking to you about this, but I'm wondering how you're doing?"
You also might want to let him know that you're at a loss about how to help him. Tell him just what you told me--that you don't want to seem insensitive or too much of a downer, but that you want to let him know that you intend to be there for him. Then ask if there's anything you can do to help him through this.
He may feel as though he doesn't want to "burden" anyone with his troubles, so let him know that you're open to listening, if he just wants to talk.
Try to be relaxed when you speak with him about this and don't tiptoe around the subject too much--that may make him feel uncomfortable. Your friend may just feel relieved to have the opportunity to talk about his cancer with someone who isn't overly morbid or pitying--someone who just acts "normal." Either way, I am sure that he will be touched to know that a good friend cares about him so much.
Take Care.
