Bidirectional relationship between the systemic immune-inflammation index and post-autologous stem cell transplantation anemia in multiple myeloma: a retrospective cohort study.

backgroundAutologous stem cell transplantation (ASCT) is a core consolidation therapy for multiple myeloma (MM). However, post-transplant anemia is a common complication that impairs recovery and prognosis. The systemic immune-inflammation index (SII), a convenient indicator of systemic inflammatory burden, is associated with prognosis in various cancers. This study aimed to investigate the bidirectional relationship between pre-ASCT SII and post-ASCT anemia in patients with MM, determine the predictive value of SII for anemia, and explore the effect of baseline anemia on inflammatory levels.

methodsThis single-center retrospective cohort study recruited 200 patients with MM who underwent their first ASCT between January 2020 and December 2025. Patients were divided into high-SII and low-SII groups (n = 100 each) based on the optimal cutoff value, which was determined using receiver operating characteristic curve analysis. The primary outcome was the incidence of anemia within 30 days of ASCT. Multivariate logistic regression and Cox proportional hazards models were used to analyze the independent predictive value of SII for anemia occurrence and recovery time. The relationship between baseline anemia status and SII levels was also analyzed using multivariate linear regression.

resultsBaseline characteristics showed that the high SII group had a significantly higher prevalence of baseline anemia (57.0% vs. 42.0%, P = 0.034). Within 30 days post-transplant, the high SII group had a significantly higher incidence of anemia (64.0% vs. 36.0%, P < 0.001), more severe anemia (moderate-to-severe anemia: 39.0% vs. 18.0%, P = 0.019), and a longer recovery time (median duration: 34.0 days vs. 16.4 days, P < 0.001). Multivariable analysis showed that high SII was an independent risk factor for post-transplant anemia (adjusted odds ratio [aOR] = 2.86, 95% CI: 1.52-5.38, P = 0.001) and was independently associated with delayed anemia recovery (adjusted hazard ratio [aHR] = 0.65, 95% CI: 0.50-0.85, P = 0.002). Reverse association analysis showed that after adjusting for relevant confounding factors, baseline anemia exhibited a trend toward association with increased log₁₀SII (β = 0.16, P = 0.085), and baseline hemoglobin level was negatively correlated with log₁₀SII (r=-0.22, P = 0.008). Subgroup analysis suggested that the predictive effect of SII on anemia was stronger in patients with ISS stage III and those who developed post-transplant infection (P for interaction < 0.05 for both).

conclusionIn patients with MM undergoing ASCT, a high pre-transplant SII is an independent predictor for the occurrence, severity, and delayed recovery of post-ASCT anemia. Baseline anemia status was associated with increased inflammatory burden. This suggests a potential bidirectional association between inflammation and anemia. SII is an easily accessible indicator that can be used to identify high-risk patients for anemia, providing new insights for optimizing peri-transplant management. CLINICAL TRAIL NUMBER: not applicable.