Eesha,
I was hoping someone else could be bothered to give some input here, but as usual, I have to address this. Yes, adults have had BMT. Elmas, from Netherlands comes to mind. Her thal minor sister was the donor. My worker had a BMT to cure lymphoma. He was in his mid 50's and almost died a couple times. He's now doing better.
The chances of success are lowered as an adult but it isn't out of the question. Much depends on the health of the patient and how much damage to organs has been done by iron.