My understanding is it's carried out with curative intent, but with the knowledge that the curative success rate isn't high.
However, even when it doesn't cure, it can significantly push back the next level treatment, and I guess NICE considered that's still a worthwhile increase in quality adjusted life years for the cost of the procedure.
You should be able to get your oncologist to confirm if my understanding is correct.
I believe this is something Mount Vernon (and other centres outside the UK) was offering experimentally, and it's relatively recently it's been recognised by NICE for treating up to 3 mets which have been found after previous curative treatment followed by recurrence. (The trial allowed up to 5 mets.)