Prognostic Value of Serum Lambda Free Light Chains in Nasopharyngeal Carcinoma

Free light chain proteins (FLCs) are small protein fragments produced by plasma cells, which are crucial for antibody production. Recently, abnormal increases in FLCs have been observed in various solid tumors, but their role in nasopharyngeal carcinoma (NPC) remains underexplored. A total of 170 NPC patients treated at Sun Yat-sen University Cancer Center from October 2018 to June 2023 were retrospectively analyzed. The X-tile tool was used to determine the optimal cutoff values for FLC levels, and Cox regression and log-rank tests were performed to evaluate the associations between FLC levels and distant metastasis-free survival (DMFS), progression-free survival (PFS) and overall survival (OS). The optimal cutoff value for serum lambda free light chain proteins (λ FLCs) in the 5-year PFS analysis were 2.1 g/L. Patients with high λ FLC levels had significantly lower DMFS and PFS rates than those with low λ FLC levels (P = 0.0144 and P = 0.0106), while OS did not differ significantly (P = 0.3735). Multivariate analysis identified pretreatment the level of λ FLC as an independent risk factor for DMFS and PFS in NPC patients. The optimal cutoff for 5-year PFS of kappa light chain proteins (κ FLCs) were 3.8 g/L, and for the κ/λ ratio, it was 2.1. No significant differences were found in DMFS, PFS, or OS when stratified by κ FLC and κ/λ values. A high serum λ FLC level is an independent risk factor for DMFS and PFS in NPC patients, indicating it may serve as a prognostic biomarker.