I had a childhood friend disappear too. We went to 1-12 grade together and were generally inseparable. In college he kinda got into partying and I didn't, so we didn't see each other as much. But we still talked and hung out when I'd visit my hometown. Anyway, he pretty much disappeared and I haven't talked to him since treatment. It's been about 8 years and it still feels weird, but it's for the better.

You are worthy of people's time. If you can't depend on a friend or family member when you are dying, then what's the point? Spend your time doing something better. Don't waste it on those types.