ASSOCIATION BETWEEN RED CELL DISTRIBUTION WIDTH AND RESPONSE TO FIRST-LINE INDUCTION THERAPY AND SURVIVAL IN PATIENTS WITH MULTIPLE MYELOMA: A SINGLE-CENTER RETROSPECTIVE COHORT STUDY IN PERU

Introduction: Red cell distribution width—coefficient of variation (RDW-CV) is relevant in evaluating multiple myeloma treatment response. Methods: A retrospective cohort study was conducted at the Hospital Nacional Edgardo Rebagliati Martins (HNERM), Lima, Peru. Patients newly diagnosed with multiple myeloma between January 2020 and June 2024 who received induction therapy were included. The primary outcomes were response to first-line induction therapy and survival outcomes. Crude and adjusted relative risks (RRs and aRRs) were estimated using robust Poisson regression, adjusting for age, sex, hypertension, diabetes mellitus, chronic kidney disease, and myeloma subtype. Hazard ratios (HRs) for overall survival and progression-free survival were estimated using Cox proportional hazards models. In secondary analyses, the optimal RDW-CV cutoff was determined using the Youden's index and interpreted as exploratory. Results: A total of 169 patients were included; the mean age was 66.9 years and 62.1% were male. The median baseline RDW-CV was 14.9% (IQR: 13.5–16.9). A favorable treatment response was observed in 74.6% of patients; 8.88% relapsed at 6 months, and 52.07% died during the 2-year follow-up. RDW-CV >14% was not associated with treatment response (aRR = 1.34; 95% CI: 0.74–2.45; p = 0.334). Elderly patients (≥60 years) and type 2 diabetes mellitus were independently associated with a higher probability of non-response. Conclusions: RDW-CV alone is not an independent prognostic marker in MM. Prospective multicenter studies with standardized thresholds are needed to define its stratification and treatment role.