Increased Bone Marrow Plasma-Cell Percentage Predicts Outcomes in Newly Diagnosed Multiple Myeloma Patients

Background Previous reports have suggested that a higher bone marrow plasma-cell percentage (BMPC%) is associated with worse outcomes. However, it is unknown whether BMPC% is an independent predictor because genetic information was not available at that time. Currently the impact of BMPC% at diagnosis of multiple myeloma (MM) is not well described. Patients and Methods We evaluated the prognostic impact of BMPC% ≥ 60% versus < 60% in 1426 newly diagnosed MM patients. All patients had an estimation of their BMPC% at diagnosis, and the highest percentage was used. Progression-free survival (PFS) and overall survival (OS) analyses were performed by the Kaplan-Meier method. Univariate and multivariate analyses for PFS and OS using the Cox proportional hazards model were performed for age, Revised International Staging System (R-ISS) score, creatinine level, and BMPC%. Results BMPC% ≥ 60% was found in 562 patients (39%), and the median PFS was shorter for these patients compared to BMPC% < 60% (22.6 vs. 32.1 months; P < .0001). Also, for OS, the median was shorter for the higher BMPC% group (53.4 vs. 75.4 months; P < .0001). On the multivariate analysis for PFS, age ≥ 65 years (hazard ratio [HR], 1.46; P < .0001), R-ISS (1-2 vs. 3) (HR, 0.49; P < .0001), and BMPC% ≥ 60% (HR, 1.23; P = .015) were predictive. On the multivariate analysis for OS, age ≥ 65 years (HR, 2.23; P < .001), R-ISS (1-2 vs. 3) (HR, 0.41; P < .0001), and BMPC% ≥ 60% (HR, 1.24; P = .02) were also predictive. Conclusion BMPC% ≥ 60% at diagnosis is predictive for PFS and OS, even in a multivariate analysis that included known prognostic factors for MM.