PB2164 PROGNOSTIC VALUE OF SERUM FREE LIGHT CHAIN IN PATIENTS WITH NEWLY DIAGNOSED MULTIPLE MYELOMA

Background: multiple myeloma is a heterogeneous disease longevity of patients from several weeks to 20 years or more. The prognosis of patients with MM differs significantly depending on the biology of the tumor substrate, the microenvironment of the bone marrow, as well as factors related to the patient's body. The search for new significant prognostic factors and their combinations is relevant for determining indications for various treatment protocols in order to increase their clinical efficacy. Aims: to assess the diagnostic and prognostic value of the study of serum free light chains (sFLC) and K/L FLC ratio (rFLC) in patients with multiple myeloma. Methods the study group included 206 patients with newly diagnosed multiple myeloma, observed in the Hematological center of the city of Novosibirsk in the period from 2012 to 2017. The median age of the examined patients was 65 years (from 29 to 76 years). All patients received bortezomib‐based CT induction courses. The concentration of sFLC‐k and sFLC‐λ (mg/l) in serum was determined by immunoturbidimetric method on a Hitachi 911 automatic biochemical analyzer using Freelite Human Lambda and Freelite Human Kappa reagents (UK). Statistical data processing was performed using the statistical software package STATISTIKA (version 7.0) and SPSS (version 23.0). Overall survival was calculated using the Kaplan‐Meier method. The significance of differences in survival in the studied groups was calculated using a log‐rank criterion (log‐rank test), the differences were considered significant at p <0.05. Results: in the analysis of FLC in patients with newly diagnosed MM, the abnormal κ/λ FLC ratio (rFLC) was observed in 99.3% of patients, which indicates a higher sensitivity of the analysis of serum FLC compared with the standard immunochemical study. The rFLC < 0.04 or> 65, as well as the sFLC‐k and sFLC‐λ levels above the median obtained for the group as a whole (sFLC‐k ≥702 and sFLC‐λ ≥493.2) correlate with the known adverse factors prognosis for MM (with a high level of microglobulin β2 (> 3.5 mg/l) (r = 0.46, p <0.001), plasma cell infiltration of BM> 24% (r = 0.42, p <0.001), renal failure (creatinine> 176 μmol/l) (r = 0.38, p <0.002), as well as with a high level of LDH (> 450 U/l) (r = 0.52, p <0.001)) and is associated with a poor prognosis. rFLC <0.04 or> 65 is associated with a high risk of mortality. Median OS in the group of patients with rFLC < 0.04 or> 65 was 35 months compared with 60 months in the group with rFLC 0.04 ‐ 65 (p <0.001), 5‐year OS ‐ 42% and 75%, respectively (p <0.001). The PFS median was 15 and 58 months (p <0.001), and the 5‐year PFS was 0% and 58%, respectively (p <0.001). Summary/Conclusion: thus, studies have shown that the determination of FLC in the serum of patients with MM increases diagnostic capabilities and can be used to assess the prognosis of survival. The value of the rFLC <0.04 or> 65 allows to divide patients with MM into risk groups with significantly different outcomes and can be used to identify patients with high risk who need more aggressive therapy and detailed monitoring of the response.