It is significantly less dependent on muscle mass, although acute inflammation, large tumor cell burden, thyroid disease, and corticosteroid use can falsely increase cystatin C levels.20 Although widespread use of cystatin C has been hindered by prolonged turnaround time,21 use of GFR estimating equations that incorporate both cystatin C and creatinine is generally preferred in patients with cancer.22 The gene discussed is CST3; the disease is neoplasm.