That's tough when you are already facing cancer. Yes, I would be mad too. The bureaucracy of American medicine is famous for this type of situation. You can get mad but I don't know what that's going to accomplish.
I would wish for an apology but I would be shocked if one was forthcoming. Don't turn this into a "John Q" situation -
https://www.imdb.com/title/tt0251160
My family's experience is that insurance fubars cancelling procedures is not unusual.
As said before, you might want to look for another doctor.