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.