Serum free light chains for monitoring multiple myeloma

[Evaluation and comparison of prognostic value of serum free light chain ratio/difference in patients with newly diagnosed multiple myeloma]

目的

比较评估初诊时血清游离轻链比值（rFLC）及差值（dFLC）对多发性骨髓瘤（MM）患者预后的价值。

方法

收集整理2012年1月至2016年3月有FLC检测记录的479例初治MM患者的相关临床资料，采用四分位间距法将rFLC、dFLC进行分组。将rFLC分别为3组：≤14.828、14.828~364.597、≥364.597。将dFLC分为3组：≤112.85 mg/L、112.85~2 891.83 mg/L、≥2 891.83 mg/L。随后分别对不同分组进行预后分析比较。使用Kaplan-Meier进行无进展生存（PFS）和总生存期（OS）比较，使用Cox回归进行单因素、多因素预后相关性分析。

结果

不同截断范围rFLC或dFLC患者的OS及PFS差异均有统计学意义。rFLC≤14.828组OS明显优于其他两组（未达到对61个月对47个月，P=0.019）；PFS与rFLC 14.828~364.597组相比，差异无统计学意义（P=0.227），与rFLC≥364.597相比，差异有统计学意义（P=0.024）。dFLC≤112.85 mg/L组与其他两组相比PFS、OS差异均有统计学意义。单因素、多因素分析显示rFLC仅与患者OS显著相关，而dFLC与患者OS、PFS均显著相关。4年OS率比较，rFLC≤14.828组4年OS率达90.84%，明显高于其他两组（59.29%、62.26%）；dFLC≤112.85 mg/L组4年OS率达89.97%，明显高于其他两组（41.32%、71.95%）（P<0.05）。

结论

对于初治MM患者，不同截断范围的rFLC、dFLC对患者生存预后影响不同。其中rFLC≤14.828或dFLC≤112.85 mg/L，其生存预后差异更为明显，且具有更低的死亡风险，危险比也更低。以此截断值判断患者预后较为理想。

Immunodiagnostic capabilities of anti-free immunoglobulin light chain monoclonal antibodies

Overproduction of plasma cell-derived monoclonal free kappa or lambda immunoglobulin light chains (FLCs) is a hallmark of multiple myeloma, AL amyloidosis, and light chain deposition disease. Because these components serve as unique cellular and serologic biomarkers, their detection and quantitation has diagnostic, therapeutic, and prognostic import. In this regard, we have developed monoclonal antibodies (mAbs) that specifically recognize the kappa or lambda FLC products of all known human variable and constant region light chain genes. We now report the results of our studies that have demonstrated the capability of these reagents to measure, in a modified fluid-phase capture enzyme-linked immunosorbent assay (ELISA), serum kappa and lambda FLCs at concentrations as low as 5 and 15 ng/mL, respectively. The mAb-based ELISA has greater sensitivity and reproducibility than does the commercially available immunoturbidimetric assay that uses polyclonal anti-FLC antibodies. In addition, the mAbs can immunostain monoclonal FLC-producing plasma cells and pathologic light chain-related amyloid and nonfibrillar tissue deposits. Our anti-FLC mAbs, with their high degree of reactivity and versatility, may provide an invaluable tool in the diagnosis and management of light chain-associated disease.

Intérêt du dosage des chaînes légères libres d'immunoglobulines sériques pour le diagnostic et le suivi des gammapathies monoclonales

PURPOSE

Monoclonal immunoglobulin free light chains (FLC) are present in the serum and urine of many patients with monoclonal gammopathies. In this review, we discuss the usefulness of serum FLC determination for diagnostic, prognostic and monitoring of multiple myeloma (MM), AL amyloidosis and monoclonal gammopathies of undetermined significance (MGUS).

CURRENT KNOWLEDGE AND KEY POINTS

Serum FLC assay is a useful laboratory test for management of light chain MM, non-secretory MM and AL amyloidosis. Currently, serum FLC testing cannot be recommended for monitoring intact immunoglobulin multiple myeloma. Even though serum FLC determination give a better risk stratification for MGUS, systematic serum FLC assay should not be used in routine because of high MGUS occurrence in the general population.

FUTURE PROSPECTS AND PROJECTS

Further prospective studies with large cohorts of patients should provide additional evidence for the role of serum FLC measurement in patients with intact immunoglobulin multiple myeloma.

The tumor kinetics of multiple myeloma following autologous stem cell transplantation as assessed by measuring serum-free light chains

In multiple myeloma, changes in serum-free immunoglobulin light chains (FLC) are a more rapid indicator of treatment response than intact immunoglobulin due to their shorter serum half-life. The present study analysed the changes in serum FLC after autologous peripheral blood stem cell transplantation (PBSCT) in 19 patients. The majority of myeloma patients (18 of 19) undergoing PBSCT had a rapid fall in FLC concentrations. In all 11 of 19 patients with raised tumor FLC, it fell within 48 h following high-dose melphalan. In patients with monoclonal intact immunoglobulin, the tumor FLC fell quicker (median half-life 4.3 days) than the monoclonal intact immunoglobulin (median half-life 14 days). FLC recovery occurred after (13 of 19) or around the time of neutrophil engraftment (6 of 19). With a median follow up of 220 days post-transplant, 16 of 19 patients have a normal FLC ratio and 3 of 19 have an elevated tumor FLC/abnormal ratio. FLC assays provided a sensitive monitor of changes in tumor and non-tumor plasma cells after PBSCT. This assay is potentially valuable as a marker of chemosensitivity, as an indicator of residual tumor and indicated time to lymphocyte engraftment. Further follow-up is required to ascertain whether differences in the kinetics of FLC responses have any prognostic clinical utility.