Formulas Calculating Creatinine Clearance Are Inadequate for Determining Eligibility for Cisplatin-Based Chemotherapy in Bladder Cancer

Abstract

Purpose Efficacy of formulas calculating creatinine clearance (CrCl) to determine renal function eligibility (CrCl > 60 mL/min) for cisplatin-based chemotherapy has not been examined adequately in the bladder cancer population. We hypothesize these formulas may underestimate measured CrCl, and therefore the eligibility for cisplatin-based chemotherapy. Patients and Methods A database of 208 patients with unresectable or metastatic bladder cancer treated on protocol at Memorial Sloan-Kettering Cancer Center (New York, NY) with cisplatin-based chemotherapy between 1983 and 1994 was examined retrospectively. The association between measured and calculated CrCl and the ability to complete three cycles (minimum therapeutic) of chemotherapy was examined. Results Baseline measured CrCl was less than 60 mL/min in 16% compared with 12% to 44% using various formulas. Concordance between calculated and measured CrCl less than 60 mL/min was poor (range of κ, 0.14 to 0.38). In patients older than age 65, 22% had a measured CrCl less than 60 mL/min, compared with 10% to 63% calculated using various formulas. Overall, 80% completed at least three cycles of cisplatin-based chemotherapy. The ability to complete at least three cycles was statistically significantly related with a measured CrCl more than 60 mL/min (P = .02), but not with calculated CrCl more than 60 mL/min. Conclusion Current formulas estimating CrCl tend to underestimate measured CrCl, especially in those older than 65 years. Depending on the formula used, up to 44% who actually received cisplatin-based chemotherapy based on measured CrCl would be deemed ineligible at present, potentially affecting survival outcomes. Methodology for determining CrCl and/or renal eligibility for cisplatin-based chemotherapy in patients with bladder cancer should be re-examined.