system
A chat on subreddit /r/NoStupidQuestions
human
Doesn't even have to be cancer, really. *Any* major illness or significant life event can be all it takes to have nearly everyone you know exit stage left; I've had it happen twice in my life. 

It hurt worse the second time, because I was so afraid of it happening after the first time and everyone *assured* me nothing would change - but  I stopped hearing from them regularly pretty quick.
gpt
That’s so horrible I am so sorry. I’m lucky then, I’m not sure I could’ve handled that with everything else going on.