Drug dosing of chemotherapeutic agents is been area of complexity in managing patients with cancer and kidney disease. Cockroft-Gault (CG) formula has been classically used for calculating drug dosing as it was used in the drug development trials. But again, CG formula doesnot account for the non-kidney determinents  of serum creatinine and this formula was developed using the non-IDMS based creatinine values in comparison to 24 hr urine CrCl. The newer equations like MDRD and CKD-EPI did not include cancer population during thier development. Cystatin C gets effected by the factors such as inflammation, steroid use and hypothyroidism which can coexist in patients with cancer. Although it has been proposed the CKD EPI-CysC equation could be the best available go to formula, there have been questions around this as well. The standard methods of mGFR using exogenous markers is complex and are not patient friendly. 

What is your practice when it comes drug dosing calculation of the highly nephrotoxic chemo agents and how frequently do you monitor the kidney functions in such cases?