Plasmablastic Morphology Is an Independent Predictor of Poor Survival After Autologous Stem-Cell Transplantation for Multiple Myeloma

Abstract

PURPOSE: To study the prognostic value of plasmablastic morphology after autologous stem-cell transplantation for relapsed or primary refractory myeloma. PATIENTS AND METHODS: Seventy-five patients were studied. Investigators blinded to the clinical details of the individual cases reviewed bone marrow aspirate slides to determine plasmablastic classification. Plasmablasts were defined using strict, well-described criteria. Plasmablastic morphology was considered to be present (plasmablastic myeloma) when 2% or more plasmablasts were present in the plasma-cell population. RESULTS: Patients underwent transplantation 5 to 88 months (median, 20 months) after the initial diagnosis of myeloma. Twenty-eight percent of patients had plasmablastic morphology. A significantly greater proportion of patients with plasmablastic morphology had abnormal cytogenetics compared with those with nonplasmablastic classification (73% v 31%, respectively; P = .003). The overall survival rate measured from the time of transplantation was significantly worse in patients with plasmablastic morphology compared with those without (median survival time, 5 months v 24 months, respectively; P < .001). Progression-free survival time was shortened also, with a median time of 4 months compared with 12 months, respectively (P < .001). In the multivariate analysis, plasmablastic classification was the most powerful prognostic factor after transplantation for both overall (P = .001) and progression-free survival rates (P < .001). We also identified three risk groups based on plasmablastic morphology: plasma-cell labeling index, lactate dehydrogenase, and cytogenetics. The median overall survival time was 38 months when none of these factors was abnormal, 17 months with one abnormal factor, and 8 months with two or more abnormal factors (P < .001). CONCLUSION: Plasmablastic morphology is a powerful independent predictor of poor survival rate after autologous stem-cell transplantation for relapsed or primary refractory myeloma.