Renal Response in Patients with Relapsed Refractory Multiple Myeloma: Interim Data of a Large, Observational, Prospective Study

Introduction:Renal impairment (RI) is a common complication of multiple myeloma (MM). Almost 20% of patients (pts) present with RI at diagnosis, while approximately 40%-50% of pts will develop RI during the course of their disease. However, there is little information on the renal response of pts with relapsed refractory MM (RRMM) receiving treatment with new drugs in clinical practice.

Aims: This is an observational, prospective, multicenter study conducted in pts with RRMM and RI (defined as an estimated glomerular filtration rate [eGFR] < 50 mL/min) to evaluate renal response to the administered therapy in pts with moderate (creatinine clearance [CrCl] 30-50 mL/min) or severe (CrCl < 30 mL/min) RI. Secondary objectives include MM response rate, overall survival, safety, and health resource utilization. We present results from an interim analysis 4 mos after completion of the inclusion period (cutoff: June 13, 2016).

Methods:Renal and MM responses were evaluated according to International Myeloma Working Group criteria. Both eGFR by the Cockroft-Gault (CG) and Modification of Diet in Renal Disease (MDRD) formulas were compared to analyze renal response.

Results:Overall, 312 pts (mean ± SD age 75 ± 9 yrs, 50% male, 57% in first relapse) were included in the study; 217 (70%) had moderate and 95 (30%) had severe RI, respectively. Anti-myeloma therapies administered were lenalidomide (LEN; 35% of pts), bortezomib (BORT; 21%), different chemotherapy regimens (CT; 22%), and other non-CT treatments (22%). Median follow-up was 7 mos (range, 0-39 mos). To date, 123 pts (39%) have discontinued treatment, 12% due to adverse events (AEs), and 37% have died. The main causes of death were disease progression (8.3%) and infections (6.4%). The mean baseline eGFR according to CG and MDRD formulas was 38.7/41.7 (± 8.5/11.8) mL/min in the moderate RI subgroup and 20.3/20.1 (± 8.0/10.1) mL/min in the severe RI group, with a strong correlation (coefficient 0.91) between the CG and MDRD eGFR. Overall, 13.5% (95% CI, 9.7%-17.2%) of patients had a renal response (5.8% renal complete response [renalCR], 0.3% renal partial response [renalPR], and 7.4% renal minor response [renalMR]) according to the CG formula while responses measured by the MDRD formula, were 17.3% (9.9% renalCR, 0.3% renalPR, and 7.1% renalMR). Median time to best renal response was 1.8 mos (range, 0.5-8.9 mos). After adjusting for demographic and clinical characteristics, there were no significant differences in GFR improvement between pts receiving LEN- and BORT-based treatments (P = 0.706). Arterial hypertension and female sex were statistically significantly associated with poor renal response. The overall MM efficacy response rate (≥ PR) was 33.4%, achieved after a median of 3.4 mos (range, 0.07-37.8 mos). For pts receiving BORT and LEN, respectively, the overall response rates were 43.5% and 44.8%, whereas only 23% of pts receiving CT achieved at least PR. Progression-free survival was 13.3 mos with LEN-based, 6.8 mos with BORT-based, and 7.5 mos with CT-based therapies (P = 0.006).

Conclusions: Preliminary results of this study in pts with RRMM and RI show that LEN- and BORT-based therapies are the regimens most commonly used in clinical practice in these pts. Overall, these therapies can improve RI in approximately 13% of cases, with no differences seen in renal function improvement between LEN- and BORT-based treatments.