Evaluation of carboplatin dosing in non-small cell lung carcinoma patients using Calvert formula and Cockroft and Gault equation for glomerular filtration rate estimation

The aim of this study was to evaluate the reliability of the Cockroft and Gault (CG) equation for glomerular filtration rate (GFR) estimation in carboplatin dosing based on the Calvert formula. The records of 117 patients with advanced non-small cell lung carcinoma treated with carboplatin were retrospectively analyzed. Theoretical carboplatin doses derived from the Calvert formula using the CG equation were calculated for each chemotherapy cycle. Fluctuations in the theoretical carboplatin doses were analyzed, and discrepancies between actual carboplatin doses prescribed by the physician and theoretical doses were assessed. It was found that, compared with the first-cycle dose, subsequent theoretical doses were more than 10% higher in 79/320 cycles (24.7%) and more than 10% lower in 53/320 cycles (16.6%; P=0.015). A body mass index greater than or equal to 30 was associated with a tendency for increased CG-estimated GFR during subsequent chemotherapy cycles (P=0.009). Physicians tended to lower the prescribed dose (32.2% of the cycles) by using a higher serum creatinine (Scr) level for dose calculation than was actually measured. We concluded that Calvert formula-derived carboplatin doses fluctuate widely during repeated cycles when actual Scr is used for CG-estimated GFR. The measurement of 24-h creatinine clearance is advised as an alternative in selected patients with reduction in serum creatinine observed during treatments.