"One gets the feel of patients, whether they want the truth or not. Usually it is best to await their approach, and often the form of question helps to determine the answer. One of my best patients and friends-an intelligent, inquisitive and humorous old man-asked me no single question about his trouble during a long illness with an inoperable cancer of the bowel. Sometimes the near relatives can help, but usually it has to lie between doctor and patient. A dear old lady of 80 said, "tell me doctor I'm not afraid"; so I told her and for the many months she lingered on she always had a smile and usually a joke. But for the many others the truth would have been mental torture.
And with Pilate one may ask, " What is truth?" At the best we can only tell some of it, for we never know the whole.'
Peripatetic The Lancet 1948
I think the important points here are that one always takes one cue from the patient ('best to wait their approach'), and one always tells the truth even if not the whole truth.