I think sometimes leaving it be can be best in the long run. My father has prostate cancer and has had no treatment other than they monitor it. He has had it for 9 years now - he is 81. My father in law had prostate cancer at the age of 64 and "opted" for an operation, sadly the cancer spread and he died at 65.
My own father believes that sometimes having an operation causes the cancer to spread.
So perhaps given your fathers age, it is as well for them not to rush into an operation or other radical treatment.
I wish both him, you and your family well