There's every reason to believe that he will lick leukemia again. Treatment for the disease, even in its more virulent adult form, has progressed substantially. He's still young and in great physical condition. He can withstand the rigors of the treatment with much greater chances of success then someone older. The five year survival rate for people in his category is 65% overall, but I could not find the rate for those doing a second round of treatment.
So, good luck, Joe! Beat it again! We're all behind you!