Yes, I was asked that question by a very knowledgeable and respected trainer (thanks Dave M.) as we crossed the pond while I was being checked out on ETOPS some years ago.
His advice, in the event of an UNCONTROLABLE fire and unable to reach an alternate, was to descend to FL250 and depressurise, as stated by Prof2 and Slasher.
In the circumstances described, I do not think that Checkboards concerns are a consideration.
It’s a choice between definitely dying or maybe surviving.