My dad has stage4 melanoma that spread to the lungs, gall bladder, bladder& brain, age 71 has diabetes, what are his survival rates?

Too many Variables: I am sorry to hear of your family's struggled. But we do not have any concrete information about your father's health condition. This is a question to ask of his doctors directly.

Not good: Stage 4 melanoma is very bad and I am very sorry about your father. Have you talked to a cancer doctor yet? If your father is in pain or having mental problems because of the spread to the brain there is palliative care available. Perhaps a discussion with hospice or a palliative care physician would be helpful at this point. God bless you.