Reversibility of Renal Impairment of Multiple Myeloma Patients Treated with Bortezomib-Based Regimens: Identification of Predictive Factors.

Renal impairment (RI) is a frequent complication of multiple myeloma (MM) and a major management problem. Previous studies have shown that bortezomib is active and well tolerated in MM patients with RI and can be associated with improvement of renal function. The purpose of our analysis was to identify factors that may predict for renal impairment reversal in patients treated with bortezomib-based regimens. Over the last 5 years, 149 either newly diagnosed or relapsed/refractory MM patients received bortezomib-based regimens in our center. Our analysis is based on 46 consecutive patients with newly diagnosed (n=10) or relapsed/refractory (n=36) MM who presented with RI defined as creatinine clearance (CrCl) < 50 mL/min. Median CrCl was 23 mL/min (range 6 to 48), 34 (74%) had a CrCl<30 ml/min and 9 patients required renal dialysis. Sixteen patients (35%) had light chain only myeloma, elevated LDH>300 IU/L was found in 24%, more than 2 gr/day of Bence Jones protein in 20 (44%) and kappa to lambda free light chain ratio was ≥8 or ≤0.125 in 25%. Patients received bortezomib (B) at standard dose and schedule, plus dexamethasone (D) (16 patients, 35%), or BD in combination with other agents such as thalidomide, doxorubicin or melphalan (30 patients, 65%). Renal complete response (RCR) was defined as a sustained increase of CrCl to >60 mL/min after treatment. Renal partial response (RPR) was defined as an increase of CrCl by 50% and with improvement of renal function by at least one stage (stage IV: <30 mL/min, stage III 30–59 mL/min) but with a post treatment CrCl < 60 mL/min. RCR was documented in 22% of patients and RPR in 22% of patients. Thus, renal response (RCR + RPR) occurred in 20 patients (44%). The median time to renal response was 11 days (range 8 to 41). Among 9 patients who required dialysis 2 patients became independent of this procedure after the second cycle of treatment. The objective response rate (at least partial response) of the myeloma was 63%. Toxicities were similar to those seen in myeloma patients without renal failure who were treated with bortezomib-based regimens. Previously untreated patients (80% vs 33% for pretreated patients, p=0.012) and those with light chain only myeloma (69% vs 30%, p=0.012) had a higher probability to achieve renal response. Response of MM to treatment was also associated with higher rate of renal response (55% vs. 24% for non-responders, p=0.037). Creatinine clearance <30 ml/min (47% vs. 33% for ClCr ³30 ml/min, p=0.410), age>75 years (p=0.309), corrected serum calcium ≥10,5 mg/dl (p=0.428), Bence Jones proteinuria ≥2g/day (p=0.167) or type of bortezomib regimen (BD or BD plus other agents, p=0.222) did not significantly affect the probability of renal response. Seventeen percent of patients presenting with RI died within the first 3 months after initiation of treatment. Patients with renal response had a trend for longer survival compared to those who did not achieve a renal response (79% vs 54% alive at 1 year, p=0.150). We conclude that when bortezomib-based regimens are administered to MM patients with RI, they are associated with a clinically meaningful renal response in 44% of them. Renal response is very rapid and occurred within 2 months in all patients. Previously untreated patients and those with light chain only myeloma may have a higher probability of renal response. Moreover, patients who achieved at least a partial response of their myeloma reversed RI more frequently than non-responders. Our data were derived from an unselected patient population with severe renal failure in more than two-thirds and with 20% of patients on dialysis. They provide further evidence that bortezomib-based regimens have a unique role in patients with RI.