Impact of weight and creatinine measurements in carboplatin dosing.

Abstract

e13027 Background: Controversy surrounding weight in Carboplatin dosing is still current. Also, new methods of measuring serum creatinine have raised more questions regarding the precision of Carboplatin dose calculations. The two objectives of this study were to evaluate the impact of alternative weight indicators (actual and adjusted body weight) in the Cockcroft–Gault equation and the use of different creatinine measurements (standard and IDMS) in order to accurately predict Carboplatin dose. Methods: We performed a retrospective chart review on all patients who received at least one dose of Carboplatin between March 7th and May 8th 2010. The patients were divided into two groups according to their body mass index (BMI): 20 < BMI < 27 and BMI ≥ 27. The differential creatinine clearance and Carboplatin dose were assessed in each group using the actual body weight and the adjusted body weight with IDMS creatinine. Moreover, for patients who had their creatinine measurement at the CHUM hospital, we calculate the difference in Carboplatin dose by using the standard creatinine (SC) measurement and IDMS creatinine with the same weight. Results: A total of 95 patients, representing 119 Carboplatin doses, were included in the analysis. 82% were women and median age was 63. The average BMI was 26,6. The Carboplatin expected AUC was 5 for 89% of patients and Carboplatin was associated to Paclitaxel in 78% of patients. In patients with a 20<BMI< 27 (44%), the average difference between the calculated dose using their actual body weight and adjusted body weight was +6.03% (95% CI, 5.2 to 6.9%). For patients with a BMI ≥ 27 (43%), the mean dose difference was +20.6% (95% CI, 18.8 to 22.5%). The use of SC or IDMS creatinine led to a discrepancy in doses of 5.2% (95% CI, 4.7 to 5.7%) for patients with BMI <27 (35 patients) and 5.5% (95% CI, 4.9 to 6.2%) for those with BMI ≥ 27 (23 patients). Conclusions: Based on these findings, we decide in our clinic, to use the actual body weight for patients with a BMI between 20 and 27, and the adjusted body weight for those with a BMI ≥ 27. We also chose not to modify our doses based on the type of the serum creatinine measurement.