The accuracy of estimating equations for the evaluation of kidney function in adult survivors of unilateral, nonmetastatic, non-syndromic Wilms tumor: A pilot study from the St. Jude Lifetime Cohort Study.

Background: Adult survivors of unilateral, nonmetastatic, non-syndromic Wilms tumor (WT) treated with whole abdomen radiation therapy (WART) are at risk for impaired kidney function. The impact of bias and accuracy on estimated glomerular filtration rate (eGFR) among adult survivors of WT has not been well documented.

Procedure: We clinically evaluated male and female WT survivors with creatinine and cystatin C, calculated eGFR using the Chronic Kidney Disease-Epidemiology equations with and without cystatin C, and measured Tc diethylenetriamine pentaacetic acid (DTPA) plasma clearance. WT survivors treated with unilateral nephrectomy (UN), non-nephrotoxic chemotherapy (NNC) and WART or treated with UN, no radiation therapy, and NNC were enrolled. Correlations between Tc DTPA clearance and eGFR were calculated. Bias and the percentage of eGFR calculations that differed from the Tc DTPA clearance by 10% or less (P) or 30% or less (P) (accuracy) were calculated.

Results: Among female WT survivors, none of the eGFR calculations was statistically significantly correlated with Tc DTPA clearance. Among both unirradiated and WART-treated male WT survivors, Tc DTPA clearance correlated well with eGFR calculations that included creatinine. eGFR calculations that included creatinine were positively biased among female participants compared to Tc DTPA clearance, and no P was greater than 90% among either irradiated males or females.

Conclusions: Among female survivors of unilateral, nonmetastatic, non-syndromic WT who have undergone UN, eGFR is poorly correlated with, is positively biased, and lacks sufficient accuracy, compared to Tc DTPA clearance.