Hi, Kelly.
I wanted to offer some words of encouragement as a transplant survivor. I had a bone marrow transplant for MDS in 1998 at age 43--much the same situation as you are in except that my MDS hadn't yet transitioned to AML. From what I've learned over the years, I think your doctor is correct in saying that a transplant for relapsed AML would be more difficult than doing it before you have more chemo. Since you have a matched sibling donor, the prospects of curing your AML via transplant are very good.
You can read about my experience
here, but keep in mind that what I describe happened almost 10 years ago. Treatments have improved so they are less harsh and more effective, and patient care has improve so they are much better at keeping you comfortable and spotting potential problems before they get out of hand.
Will you have your transplant at Univ. of Maryland? Post any questions you have in this thread, or send me a private message if you'd like to talk offline.
Best regards,
Ruth Cuadra