I have not had cancer, but at 66 I have been through the mill often enough to say with confidence, when the going gets rough, how well you make it, or whether you make it at all, is closely tied the quality of your support network.
If you are facing cancer or some other apparent calamity yourself, and you don't already have a support network, a team of people helping you pull through, build one. Now. Even if it means saying to a relatively casual acquaintance, "This is what I'm going through. I need a support network. I don't have one. Can you just sit and listen to me?"
If you are part of someone else's support network, let your words be few. Your presence and listening ear are what matter most.
So be it.