Hi Sharron,
as the others have said, this makes no sense at all and I am pretty sure someone has misunderstood something. You say that the doctor isn't going to refer him anywhere so was he told by the GP about this diagnosis or did he actually attend a hospital appointment? Have you seen the tablets he is on? Could it be 3 weeks of hormones rather than 3 days of vitamins? Or a three monthly injection of hormones?
The oncology services just don't tell someone they are terminally ill and send them home - well sometimes they might but then patients and families quite rightly kick off - there would be hospice services, palliative care, pain control all to discuss or refer on for. You don't say much about your dad's state of health - his age, whether he is in great pain, whether he has other medical problems?
It just sounds wrong - I hope you can get a bit more of the story for us.