Hello and thank you for your question,
I am sorry to hear your dad's prostate cancer is back.
HIFU is a relatively new treatment (5 years) and is not yet approved by FDA to be used in the United States as treatment for prostate cancer.
When you go back to see the urologist, you can ask the urologist to perform nuclear bone scan and CT scan of the abdomen and pelvis on your dad to make sure the cancer has not metastasized.
If it hasn't (and chances are it has not), I would recommend consulting with the urologist to see if your dad is a candidate for radiation therapy (which is still the best treatment option considering your dad's age) or a candidate for radioactive seed implant (2nd to radiation).
Other options include getting hormonal injection, called Lupron, every 4 months. This does not kill cancer but stops it from growing. It has a lot of side effects that your dad needs to be aware of before starting (hot flashes, breast enlargement, erectile dysfunction).
I hope you find this information helpful. Please feel free to follow-up with any other questions you might have.
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Best wishes and good luck,