Renal dysfunction within 90 days of FluBu4 predicts early and late mortality.

Myeloablative conditioning regimens with significant extramedullary toxicity result in high rates of renal dysfunction including acute kidney injury (AKI). Here we examine the incidence and impact of a reduced creatinine clearance (below 60 ml/min) before day 90 (early renal dysfunction, ERD) in patients receiving the reduced toxicity fludarabine/i.v. busulfan (FluBu4) regimen prior to allogeneic transplant. Of 91 patients receiving FluBu4, 62 (68%) developed ERD. ERD resulted in worse overall survival (OS, 2.2 years versus median not reached, p = 0.04) and progression-free survival (PFS, 1.6 years versus median not reached, p = 0.02). This was due to a higher relapse rate (34% versus 14%, p = 0.03) in the ERD group. In time-dependent Cox proportional hazards models adjusted for age, ERD was associated with worse OS (hazard ratio [HR] 2.67, 95% confidence interval [CI] 1.06-4.21, p = 0.043) and PFS (HR 2.52, 95% CI 1.17-4.28, p = 0.030). Patients with ERD surviving 1 year had an increased risk of chronic kidney disease (CKD, OR 10; 95% CI 1.4-112.6, p = 0.0181), which was associated with worse survival (3.2 years versus median not reached, p = 0.002). ERD after FluBu4 is therefore a poor prognostic sign resulting in increased relapse, worse OS, and high risk of CKD at 1 year.