Is a doctor obliged to tell a patient their prognosis?

[CUFGDS]

During my work experience my doctor explained to me how hard it is to break the news to some one that is terminally ill... I went on and wrote about this in my personal statement. My form tutor read my personal statement and during a line where I said a doctor must make their patients aware of their situation she pointed out that this is not the truth, but did not explain, she just left it at that.

So im just wondering is a doctor obliged to tell their patients of their illness despite how dire it is?

This may be a stupid question but I cant find the answer, thanks in advance for answers.

[nursepen]

A patient has the right to know his/her diagnosis and prognosis in order to make a true consent for teatment unless the patient is deemed by a psychiatrist to be mentally unstable. If one has cancer, for instance, one has the right to know the benifits and risks of any treatment modality and the right to refuse. All patients have the right to be treated with dignity. Please look up Patient's Right's and Responsibilities as well as Patient's Freedom and the HIPPA laws of privacy. I hope this helps, Penny