Introduction

Renal failure is a common complication observed in patients with multiple myeloma (MM) and other plasma cell cancers that is generally associated with an adverse clinical outcome[1]. The optimal management of MM patients with renal disease presents a challenge. As numerous drugs are cleared via the kidneys, renal impairment imposes limitation on anti-myeloma therapeutics through decreased drug clearance and enhanced toxicity[1]. Thus optimal renal function assessment is essential, often involving measurements of glomerular filtration rate (GFR), serum creatinine (sCr) levels, and creatinine clearance (CrCl) rates. However, the exact definition and incidence of “renal failure” varies among investigators and depends on the measurement parameter being used. The Kidney Disease Outcomes Quality Initiative (K/DOQI) of the National Kidney Foundation defines kidney disease as either kidney damage or a decreased GFR of <60 ml/min/1.73 m2 for ≥3 months[2]. Using the KDOQI criteria, we observed that 54% of patients seen at Roswell Park Cancer Institute presented with stage ≥3 (<60 ml/min/1.73 m2) kidney disease at the time of diagnosis[3]. When sCr is used to assess kidney function, a value of ≥2 mg/dl specifies impairment and is present in approximately 20% of MM patients[4–7]. Although measurement of sCr is simple and relatively the least cumbersome approach, it varies with age, sex and muscle mass, and is not an absolute reflection of renal function[8]. Patients with MM tend to be elderly with normal or low muscle mass and thus sCr may be lower for a given GFR or CrCl rate. As such, the extent of renal insufficiency is often underestimated in these patients when sCr alone is utilized to assess kidney function[8–13].