Grades III-IV acute GVHD. Cumulative incidence of grades III-IV acute GVHD among allogeneic HSCT patients after conventional (n = 914) or nonmyeloablative (n = 181) conditioning. Cumulative incidence rates of grades III-IV acute GVHD at 120 days after conventional (solid line) or nonmyeloablative (broken line) conditioning were 25% and 21%, respectively (P = .14). GVHD grades could not be assigned because of confounding from severe skin toxicity in 2 patients or from recurrent malignancy and premature termination of GVHD prophylaxis in 3 patients.