The renal clearance of carboplatin, which is a second-generation platinum compound, is correlated with the glomerular filtration rate (GFR). As the area under the concentration-time curve (AUC) of free carboplatin is related with efficacy and toxicity following carboplatin administration, carboplatin dosing is defined as a target AUC and generally calculated by the Calvert formula according to the patient's GFR. We conducted a survey on the usage of the Calvert formula to clarify the current situation in Japan. As a result, the value of creatinine clearance (CLcr), which is higher than GFR due to the tubular secretion of creatinine, has been used as a substitute for GFR for the Calvert formula without appropriate correction in 71 of 109 institutions, where CLcr estimated by a Cockcroft-Gault equation and/or obtained by 24-h urinary collection are used. On the other hand, body surface area-indexed values of renal function have been directly used without conversion to individual values in 42 of 71 institutions, where GFR estimated by a Japanese equation and/or CLcr estimated by a Jelliffe equation are used. It was found that the desired dosing of carboplatin has not been administered to patients in a number of institutions. Back to the original concept of the Calvert formula, it is reasonable to use a GFR estimated by the Japanese equation and converted to an individual value. In addition, we need to assess tolerability following carboplatin administration and discuss the appropriateness of the starting dose for each patient without being overly reliant on the dose obtained by the Calvert formula.
