Benefit of plasma cystatin C for carboplatin individual dosing in a patient with spinal amyotrophy.

PURPOSE: Carboplatin is used in several chemotherapy regimens and is mainly excreted by kidneys. The recommended dose is calculated using a target exposure (area under the curve or AUC) and a predicted carboplatin clearance (CLcarbo). This clearance could be obtained by equations based on the estimation of glomerular filtration rate (GFR) including serum creatinine (SCr) alone or with plasma Cystatin C (CysC). CASE PRESENTATION: A 68-years-old woman with uterine carcinosarcoma and lymph node/lung metastases should be treated by carboplatin-paclitaxel. However, her SCr level was extremely low (i.e., 10 µmol/L) due to a spinal amyotrophy. Therefore, carboplatin clearance and dose calculation was estimated from an equation based on CysC, body weight, and age but not SCr proposed by Thomas et al. A therapeutic drug monitoring was performed to determine the patient’s actual CLcarbo. RESULTS: The patient presented an actual CLcarbo close to the value predicted by the equation based on CysC (93.7 and 92.8 mL/min, respectively). The other formulae based on SCr alone or with CysC would have been associated with a substantial overestimation of her CLcarbo and thus would have led to drug overexposure. CONCLUSION: We concluded that the Thomas equation based on CysC alone represents a suitable alternative in patients with very low serum creatinine concentration due to amyotrophy.