Serum phosphate level and its kinetic as an early marker of acute kidney injury in tumor lysis syndrome.

INTRODUCTION: Acute kidney injury (AKI) is a major cause of mortality in tumor lysis syndrome. The biochemical parameters and kinetics of tumor lysis syndrome remain poorly described. Particularly, whether blood serum phosphate variations may help in the identification and management of patients who will eventually develop AKI remains to be studied. METHODS: In this retrospective study, we included patients with tumor lysis syndrome episodes without AKI at diagnosis, and analyzed serum phosphate kinetic, clinical and tumor lysis syndrome biochemical variables to identify factors associated with AKI onset, and determine threshold values of phosphatemia associated with AKI development. RESULTS: One hundred thirty tumor lysis syndrome episodes occurred in 120 patients during an 11-year period at the University Hospital of Angers. AKI developed in 56 tumor lysis syndrome episodes. In multivariable analysis, among the analyzed factors, only an increase in serum phosphate levels (before AKI diagnosis), exposure to platinum salts and an increase in LDH levels were associated with AKI development. Before AKI onset, a serum phosphate cut-off of 2.1 mmol/L was not effective in predicting AKI development (sensitivity 48%, specificity 84%, area under the receiver operating characteristic curve (AUC) 0.63 [0.52-0.74]). No other biochemical parameters were effective to better predict AKI occurrence. CONCLUSION: This work suggests that increases in serum phosphate and LDH appear to be early and reliable biomarkers of AKI in tumor lysis syndrome. No valuable threshold value of serum phosphate was found to effectively predict AKI. This work is the basis for further prospective controlled studies on phosphate monitoring and phosphate lowering therapies to prevent AKI during tumor lysis syndrome.