Free Light Chain Ratio As a Simple Prognostic Marker in a Single Institution Experience

Multiple myeloma (MM) is a plasma cell dyscrasia characterized by bone marrow plasma cell infiltration and the secretion of monoclonal immunoglobulin (Ig) in the serum or urine. Median survival in MM patients is approximately 5 years and significant morbidity may be experienced. The course is progressive and although, always incurable, the prognosis is highly variable. The two more widely used staging systems in MM are by Durie and Salmon and the International Staging System (ISS). Others have been studied, including serum free light chain (sFLC) concentrations and ratio (sFLCr).

Methods: We measured sFLC in 27 newly diagnosed MM (21 Intact Ig MM, 5 light chain MM, 1 non secretory MM) at our center (Hospital del Salvador, Santiago de Chile) from October 2013 until June 2015. The sFLCr was calculated with the involved monoclonal light chain as the numerator. The median sFLCr was 17. Patients were divided into a "low group" (<17 sFLCr) and a "high group" (>17 sFLCr). We also analyzed these patients using the cut off (sFLCr of 50) previously reported by Garcia de Veas Silva et al. [Hematology reports 2015; 7 (s1) p23] The median follow-up was 16 months.

Results: During the period of study there were 8 deaths (29,7%). Seven (87,5%) of these deaths presented with an ISS score of 3 (table 1). Mortality rates were lower in the group of patients with "low" sFLCr (15,3%, 2 deaths in a group of 13 patients), as compared to patients with a "high" sFLCr (42,9%, 6 deaths in a group of 14 patients) (table 2).

Using the cutoff established by Garcia de Veas Silva et al, the mortality rate for patients with sFLCr >50 was 66,7% vs. 11,1% in for patients in the <50 sFLCr group (table 3).

Discussion: Although a short follow up period was available for analysis, we believe these results are promising. sFLCr can be used as an easy prognostic indicator in newly diagnosed, symptomatic MM, especially when high risk patients (>50 sFLCr) are identified. The introduction of biomarkers in the evaluation of MM patients will enable better risk assessment and rational follow up.