Total kidney volume as a predictor of measured glomerular filtration rate in patients with solid tumors: a prospective cross-sectional analysis.

Background: Although previous data demonstrate that total kidney volume (TKV) correlates with measured glomerular filtration rate (mGFR), evidence is however scarce in the oncology setting. The aim of this is study is to evaluate whether adding TKV to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimating equations improves the prediction of measured glomerular filtration rate (mGFR) in patients with cancer.

Methods: We evaluated patients with solid tumors between April 2015 and September 2017 who had undergone contrast computed tomography and GFR measurement through the plasma clearance of ⁵¹Cr-EDTA. Estimated GFR (eGFR) was determined through CKD-EPI equations based on serum creatinine (eGFRcr) and combined with serum cystatin C (eGFRcr-cys). We used the 2009 eGFRcr and 2012 eGFRcr-cys equations and the race-free 2021 eGFRcr, and eGFRcr-cys. TKV was measured using a semi-automatic segmentation program, excluding non-functional tissues. Linear regression models were built, with TKV and eGFR equations as predictors and mGFR as the outcome.

Results: We included 189 patients (median age 58.0 [48.0-65.0] years, 49.2% male). Median mGFR and TKV were 82.7 (66.3-94.5) mL/min and 303.1 (257.7-351.8) cm³, respectively. TKV improved the coefficient of determination (R²) when added to 2009 eGFRcr and 2012 eGFRcr-cys equations from 0.62 to 0.73 and 0.73 to 0.80, respectively. For the 2021 eGFRcr and eGFRcr-cys equations, R² improved from 0.65 to 0.75 and 0.75 to 0.82, respectively.

Conclusion: These results suggest that TKV measurement improves the prediction of mGFR in association with the CKD-EPI equations in patients with solid tumors.