By doing what the good ones have always done, getting to know the patient and their loved ones, understanding their expectations and hopes (and fears) and communicating accordingly.
In the "old days" when the consultant decided what and whether the patient should be told often (usually!) without reference to anyone else, on several occasions, I was put in the difficult situation of being asked directly by the patient "What is wrong with me? why will nobody tell me what is happening?"
I guess it happened to me more because I used to take people on home visits out of the hospital to plan discharge or breaks at home. In those circumstances, for those people, the not knowing was far more terrifying than the (admittedly bleak) truth. Of course you don't "destroy hope" and the first thing i used to do was find out what the patient usually knew or understood which was usually more than the consultant (and relis) thought, and work from there to give them the information that they wanted.
Its a slippery slope when staff are permitted or expected to lie to patients, even by omission.