This is such a difficult issue. One thing I can say is that the person with cancer is JUST AS shocked and confused as the people closest to him/her. No more, no less. That's in the first week or two. The only other difference that is very personal to the patient is FEAR. The most undescribable permanent panic-attack you can imagine. The fear subsides once the oncologists explain and decide what their plan-of-action is. Ok - that's the patient.
The people around him/her? They have to be the strong ones. Advice them to read as much possible regarding their loved-ones condition. Education is the key. It makes you understand the condition better, and gives so much hope. As people suffering from cancer often leave all in the hands of their caregivers, it is often up to the loved-ones to do the research.
Friends/family can also expect various degrees of strange characteristics from the patient. BE PATIENT!! Cancer sufferers often feel very alone in their fear. Drugs can also alter moods. To do visualisation with a sick loved-one also builds an enormous bond. Try it!
Offer help. Go with the patient to sessions, drive kids, cook, go to movies and also talk about everyday stuff, but DON'T ignore the issue at hand. Ask the patient if they want to talk 'cancer' or 'stuff' today.
And, tell your friend who's loved-one has been diagnosed, that this can be an especially sacred time in their lives together. Do all those things together that was always only talked about - but never done. Again - read, read and read some more!!!! Trust in the fact that scientists will never-ever stop in their quest to find a cure. Never.
If their is anything specific you/your friend wants to know about cancer - PLEASE let me know? I'll research and do an article on it, with pleasure!!!
Did I answer your question - or am I babbling?