The cumulative incidence of relapse for patients transplanted for CML in CP or AP categorized on the basis of BU steady state concentrations (C_SSBU) greater than or less than the median (917 ng/mL) during conditioning. Patients were censored on the date of last cytogenetic examination. One patient who died on day 34 did not have any posttransplant cytogenetic examinations and was not evaluated for relapse. Tic marks denote patients at risk of relapse. The difference between the groups is statistically significant (P = .0009).