An elevated systemic inflammation index is related to an inferior response to pomalidomide and dexamethasone treatment in patients with relapsed and refractory multiple myeloma

The systemic inflammation index (SII) might serve as an indicator of the equilibrium between the inflammatory and immune responses. The aim of the study was to determine the clinical value and prognostic significance of SII in the cohort of multiple myeloma (MM) patients treated with a regimen of pomalidomide and dexamethasone (Pd). This retrospective, real-life study included patients who received a Pd regimen in our centre between November 2018 and July 2022. The systemic inflammation index was calculated from peripheral blood counts of platelets, neutrophils, and lymphocytes collected shortly before commencement of Pd treatment using the equation: SII = N × P/L, where N, P, and L are the respective counts litre of peripheral blood for neutrophils, platelets, and lymphocytes. The study group consisted of 54 patients. Most patients received Pd as the third (38.9%) or fourth (37.0%) line of treatment. The median number of completed treatment cycles was 5 (IQR: 1-12). The median progression-free survival (PFS) was 6.8 months and overall survival (OS) 14.8 months. High SII (> 374) was an independent prognostic factor for PFS (HR = 3.0, 95% CI: 1.4-6.3, < 0.01) and OS (HR = 2.2, 95% CI: 1.0-4.6, = 0.04). In the low SII group, the respective median PFS and OS values were 9.6 and 21.7 months, compared to 2.6 ( = 0.018) and 5.5 months ( = 0.035) in the high SII group. The systemic inflammation index has prognostic significance in MM patients treated with Pd. A high SII predicts a poorer outcome in pretreated MM patients undergoing Pd treatment evaluation. As such, it may well be a key factor for guiding subsequent treatment decisions.