Performance of CKD-EPI-estimated glomerular filtration rate (eGFR) in patients with bladder cancer (BC)

Objectives Cisplatin/Carboplatin are essential components of BC chemotherapy. The commonly compromised renal function in BC patients necessitates close GFR-based dosing guidance for chemotherapy with these agents. The easily obtained serum creatinine (SCr) based GFR-predicting equations are generally inaccurate compared to exogenous tracer clearance techniques. We explore the accuracy of CKD-EPI-eGFR vs GFR measured by plasma clearance (mGFR) as the standard, in BC patients.

Methods In 28 men with BC, aged 66.5±6.0 yrs, scheduled to receive chemotherapy, baseline eGFR was obtained by the CKD-EPI equation based on SCr (IDMS) and patients demographics and mGFR was calculated from Cr-51-EDTA single injection, 4-hour plasma clearance curve. eGFR-mGFR correlation and agreement and eGFR precision and accuracy were assessed by proper statistics.

Results eGFR and mGFR did not differ significantly (66.2±29.3 vs 62.5±25.2 ml/min, p=0.168), correlated well (r = 0.877, p<0.001) but agreed loosely (95% CI -31.2 to 20.7 ml/min, Bland-Altman analysis). Compared to mGFR, eGFR precision and 10% and 30% accuracy were -3.8±14.1 ml/min, 30.5% and 75.1% respectively.

Conclusions Patients with BC have reduced baseline renal function and eGFR is not an accurate measure of the true, measured GFR. As, based on eGFR, a considerable percentage of patients will be under- or overtreated, baseline mGFR should be routinely obtained in BC patients scheduled for cisplatin/carboplatin chemotherapy.