Chronic GVHD by conditioning regimen intensity. The 2-year incidence of chronic GVHD was 62% (95% CI, 58-66) for Bu4/Cy, 60% (95% CI, 55-64) for Flu/Bu4, 42% (95% CI, 36-48) for Flu/Bu4 + ATG, 52% (95% CI, 47-57) for Flu/Bu2, 44% (95% CI, 37-50) for Flu/Bu2 + ATG, 56% (95% CI, 49-63) for Flu/Mel, and 31% (95% CI, 20-43) for Flu/Mel + ATG.