Very sad to hear this. He's already beat it back twice. The first time through chemo, and he had a stem cell transplant last year. Stem cell transplants are usually the last resort, cutting-edge treatment. When it works, it works well, but when it doesn't, the cancer is probably an extremely aggressive one.
(My mom had a stem cell transplant to treat a similar blood cancer, and it gave us another 2 wonderful years with her, but as with Viv's cancer, hers was very aggressive and came back with a vengeance.)
I do hope Viv will make a full recovery, as he's still relatively young, but after a stem cell transplant, i'm not sure how many other successful treatment options there are.