Reliability of predicted renal function in Japanese patients on cisplatin therapy

Cisplatin, cis-Dichlorodiammine platinum (II) (CDDP) remains a major antineoplastic drug for the treatment of solid tumors. Its chief dose-limiting side effect is nephrotoxicity. To make a safe and effective dosing regimen of a drug excreted mainly by the renal route, evaluation of patients' renal function is essential. Creatinine clearance (CLcr) or glomerular filtration rate (GFR) is considered to be a standard renal-function test. Several equations have been used in clinical settings, to predict CLcr and GFR using serum creatinine concentration. We carried out a retrospective analysis of the correlation between 24-hour CLcr measured by a urine collection method; and the predicted CLcr and GFR estimated by various equations such as Jelliffe, Yasuda, Orita, Mawer, Mawer, MDRD and modified MDRD, and Cockcroft-Gault. This study used data from Japanese head-and-neck cancer patients, before and after chemotherapy with CDDP. Slopes of regression lines of scatter plots between measured CLcr and predicted renal function in post-CDDP patients were less compared to pre-CDDP patients. On the other hand, Y-intercepts were noted in the scatter plots on renal function from all equations. These results suggest that evaluation of renal function using predictive formulae may have been over-/under-estimated after CDDP administration.