During my wife's battle with cancer 20 years ago, she "coded out" two times, once when I was with her in the ICU, once on the operating table. She had the full-up near-death experience each time.
She described pretty much what you've all read in the other personal accounts of such events.
Whatever the biology, or even the physics (some have proposed a type of quantum entanglement occurs) of near-death are, I can affirm that it changed the way my wife looks at the nature of her life and existence in general. I am not unscathed by it, of course, but it is among the most deeply personal experiences one can have.
Although probably obvious, I'll close by saying my wife and I are still married and she has been cancer-free since the ordeal.