In this case, there's nothing left to do.
All the consent forms have been signed, whether it's "informed" or not remains debatable; all the well-meaning friends have sat in on meetings, although they couldn't tell you IP from IV from subcutaneous; all the available lines of communication have been tried, to no avail.
It is a helpless, frustrating feeling, this place. All of my psychology training has left me with not knowing what to do or what to say, how to react next week....because it is different when it is not a patient/client. It is different when you have a personal, familial stake in things. When you watch someone offer themselves up for sacrifice in the hopes of gaining time, under the false impression that studies have shown benefit, because they've been misinformed by the provider they trust....and chosen not to hear the information you've provided.....it is hard. It hurts.
When I watch this unfold, it reminds me of why I feel (still) so strongly about being an oncologist. So things like this don't have to happen to another person and their family. Because in medicine, decisions don't just affect the patient. You don't just work with the patient in front of you; you work with their family, whether you ever meet them or not. And this....this.....this just blows my mind. On a professional, medical, and human level.

