Abstract
Introduction: In plasma cell myeloma (PCM), tumor burden and activity plays an important role in diagnosis and prognosis (e.g. circulating plasma cells), however very little attention has been directed to the impact of the non-plasma cell component of the bone marrow. The presence of anemia has been used to distinguish PCM from smoldering myeloma; however this can be a non-specific finding as there are many potential causes of anemia besides PCM. We sought to determine if the level of erythropoiesis in bone marrow biopsies may be a more reliable prognostic factor. In the study herein, we assessed the level of bone marrow erythropoiesis in patients with newly diagnosed PCM, and compared those findings with cytogenetic results (CGs), other prognostic factors and overall clinical outcome. We hypothesized that patients with adequate erythropoiesis (AEp) are likely to have favorable cytogenetics and better outcome compared to those with decreased erythropoiesis (DEp).
Methods: We retrospectively reviewed pathology database for bone marrow biopsies in patients with diagnosis of plasma cell myeloma (PCM) at Beaumont Hospital, an academic community center from 2012 and 2014. Biopsy cases without anemia were excluded. A total of 91 patients with plasma cell myeloma and anemia were identified. Each biopsy was re-examined to determine the level of erythropoiesis. The level of erythropoiesis was calculated by multiplying erythroid fraction (obtained from M:E ratio) with non-plasma cell bone marrow cellularity. Cases were separated into AEp and DEp using an erythroid compartment cut-off of 7.5% based on already established data. Kaplan-Meier analysis was used to compare survival between groups.
Results: Demographic distribution of studied patients were 46 (50.1%) white, 39 (43%) African Americans and 6 (6.6%) others. Out of 91 cases analyzed, 38 (42%) had AEp whereas 53 (58%) had DEp. Among those with AEp, 23 (62%) had favorable CGs (defined as those without t (4, 14), t (14, 16), t (14, 20) or 17 p deletion); 15 (38%) had unfavorable CGs. Among those with DEp, 14 (26%) had favorable CGs whereas 39 (74%) had unfavorable cytogenetics. The vast majority of patients with favorable CGs were alive whether they had AEp (87%) or DEp (79%), thus CGs remained significant even after controlling for erythroid compartment (p = 0.03). Overall, those with AEp were noted to have significantly lower β-2 microglobulin (AEp median =2.42 mg/dL, DEp median = 4.50 mg/dL, p = 0.02). Kaplan-Meier analysis showed a significant difference in survival curves among the four groups (AEp with favorable CGs, AEp with unfavorable CGs, DEp with favorable CGs, DEp with unfavorable CGs, p<.0001). While the two groups with favorable CGs showed no significant difference (p=.6050), the two groups with unfavorable CGs did (p=.0027).
Conclusion: Our findings suggest that patients with PCM and anemia are not a homogenous population. Assessment of the erythroid compartment in these patients reveals a population with AEp that has more favorable CGs and lower β-2 microglobulin than patients with DEp. Despite this finding, patients with favorable CGs had a favorable clinical outcome whether they had AEp or not, indicating that current therapies can overcome differences in erythropoiesis in that group. For patients with unfavorable CGs, however, those with AEp had superior survival outcome compared to those with DEp, indicating that there may be some prognostic or diagnostic utility to assessing erythropoiesis in patients who meet current criteria for PCM, and possibly, incorporating erythropoietic activity into diagnostic/prognostic schema.
No relevant conflicts of interest to declare.
