Tessa:
One of the hard things about this experience is that your friends, who do care about you, are in shock, too, particularly when it's the "strong one" who's been hit.
Give them time, and if possible, give them something specific they can do for you. Those of us on the team as supporters want to participate, but it's often hard to know what to do or what to say when someone you care about is suffering. You might consider telling your callers that you just need to talk (or don't want to talk right now if that's the case); you can ask for company or e-mails or even jokes or links to net places which can make you smile.
Tonight, I picked up a prescription for my cancer survivor friend and just dropped it off at her house. She didn't want company, so I didn't stay, but I needed to DO something and was very grateful to have had the opportunity of making my caring concrete. I'll bet your friends are the same.
Hang in there!
Carol