Role of serum-free light chain assay for defining response and progression in immunoglobulin secretory multiple myeloma.

The International Myeloma Working Group (IMWG) guidelines recommend using electrophoresis and immunofixation to define response and progressive disease (PD) in immunoglobulin (Ig) secretory multiple myeloma (Ig-MM), whereas the role of serum-free light chain (sFLC) is controversial. We retrospectively analyzed the value of adding sFLC assays in the definition of response and PD according to IMWG criteria in 339 Ig-MM patients treated with a first-line novel agent-based therapy (median follow-up 54 months). sFLC PD was defined according to conventional criteria plus increased sFLC levels, or sFLC escape (sFLCe); progression/sFLCe-free survival (ePFS) was the time from the start of treatment to the date of first PD or sFLCe, or death; overall survival after PD/sFLCe (OS after Pe) was the time from first PD or sFLCe to the date of death. 148 (44%) patients achieved a complete response and 198 (60%) a normal sFLC ratio (sFLCR). sFLCR normalization was an independent prognostic factor for extended PFS (HR = 0.46, p = 0.001) and OS (HR = 0.47, p = 0.006) by multivariable analysis. 175 (52%) patients experienced PD according to the IMWG criteria, whereas 180 (53%) experienced PD or sFLCe. Overall, a sFLCe was observed in 31 (9%) patients. Median PFS and ePFS were both equal to 36 (95% CI = 32-42, and 32-40, respectively) months. sFLC PD adversely affected the OS after Pe compared to PD with increasing monoclonal Ig only (HR = 0.52, p = 0.012). Our results support the inclusion of the sFLC assay for defining response and PD in Ig-MM.

Long term follow-up of humoral and cellular response to mRNA-based vaccines for SARS-CoV-2 in patients with active multiple myeloma.

Long-term kinetics of antibody (Ab) and cell-mediated immune (CMI) response to full anti-SARS-CoV-2 vaccine schedule and booster doses in Multiple Myeloma (MM) patients remain unclear. We prospectively evaluated Ab and CMI response to mRNA vaccines in 103 SARS-CoV-2-naïve MM patients (median age 66, 1 median prior line of therapy) and 63 health-workers. Anti-S-RBD IgG (Elecsys®assay) were measured before vaccination and after 1 (T1), 3 (T3), 6 (T6), 9 (T9) and 12 (T12) months from second dose (D2) and 1 month after the introduction of the booster dose (T1D3). CMI response (IGRA test) was evaluated at T3 and T12. Fully vaccinated MM patients displayed high seropositivity rate (88.2%), but low CMI response (36.2%). At T6 the median serological titer was halved (p=0.0391) in MM patients and 35% reduced (p=0.0026) in controls. D3 (94 patients) increased the seroconversion rate to 99% in MM patients and the median IgG titer in both groups (up to 2500 U/mL), maintained at T12. 47% of MM patients displayed a positive CMI at T12 and double-negativity for humoral and CMI (9.6% at T3) decreased to 1%. Anti-S-RBD IgG level ≥346 U/mL showed 20-times higher probability of positive CMI response (OR 20.6, p<0.0001). Hematological response ≥CR and ongoing lenalidomide maintenance enhanced response to vaccination, hindered by proteasome inhibitors/anti-CD38 monoclonal antibodies. In conclusion, MM elicited excellent humoral, but insufficient cellular responses to anti-SARS-CoV-2 mRNA vaccines. Third dose improved immunogenicity renewal, even when undetectable after D2. Hematological response and ongoing treatment at vaccination were the main predictive factors of vaccine immunogenicity, emphasizing the role of vaccine response assessment to identify patients requiring salvage approaches.