Red Cell Distribution Width at Diagnosis Reflects Advanced Disease While Dynamic Changes Predict Survival at Relapse in Multiple Myeloma: A Retrospective Study.

Introduction Multiple myeloma (MM) is a complex plasma cell malignancy characterized by clonal proliferation and monoclonal immunoglobulin production. Despite the availability of several prognostic markers for MM, many are challenging to implement routine clinical practice due to cost, complexity, or lack of standardization. Red cell distribution width (RDW), a cost-effective and routinely measured parameter in complete blood counts, has gained increasing attention as a prognostic marker due to its association with disease severity and outcomes in MM. This study investigates the prognostic utility of RDW in MM, focusing on its relationship with patient outcomes, particularly in those undergoing autologous stem cell transplantation (ASCT). Methods This retrospective study included 218 patients diagnosed with MM between 2010 and 2018. Demographic, clinical, and laboratory data, including RDW levels at ASCT and first relapse, were collected. Patients were stratified into high (>16.5%) and low (≤16.5%) RDW groups. The impact of RDW levels and their changes on progression-free survival (PFS) and overall survival (OS) were analyzed using Kaplan-Meier and log-rank tests. Results Higher RDW levels at diagnosis were significantly associated with advanced disease stages, notably R-ISS stage 3 (p=0.022). While no significant survival differences were observed based on baseline RDW levels, dynamic changes in RDW from diagnosis to first relapse were strongly prognostic. Patients maintaining low RDW had the longest PFS (37 months) and OS (88.8 months), whereas those transitioning from low to high RDW experienced the shortest PFS (nine months) and OS (40.6 months). At relapse, patients with low RDW demonstrated superior outcomes (PFS: 34 vs. 14 months, OS: 81.2 vs. 40.6 months; p<0.001). ASCT markedly improved survival outcomes, with longer PFS (p=0.028) and OS (p<0.001). Higher hemoglobin levels (>10 g/dL) were also associated with extended PFS (p=0.038). Reassessing RDW prior to ASCT did not yield significant differences, suggesting that the prognostic value of RDW lies in its dynamic changes, particularly around relapse events. Conclusions RDW levels at diagnosis reflect advanced disease stages in MM but are not independent predictors of survival. However, dynamic changes in RDW, particularly from diagnosis to relapse, highlight its potential as a robust marker for monitoring disease progression and relapse risk. ASCT remains a cornerstone of MM management, significantly improving survival outcomes and complementing RDW trends in prognosis. Standardizing RDW thresholds and integrating its dynamic trends into clinical workflows could enhance risk stratification and personalized treatment strategies. Prospective, multi-center trials are essential to validate these findings and establish RDW's role in comprehensive prognostic frameworks for MM.