Prognostic Impact of Serum Heavy/Light Chain Pairs in Patients With Monoclonal Gammopathy of Undetermined Significance and Smoldering Myeloma: Long-Term Results From a Single Institution

BackgroundAsymptomatic monoclonal gammopathies, such as monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma (SMM), are clinical conditions that usually precede symptomatic multiple myeloma. Therefore, risk stratification is crucial owing to the heterogeneous progression rate among these patients. In previous years, suppression of the uninvolved chain of specific heavy/light chain (HLC) pairs in serum has been identified as a new risk factor in MGUS. The aim of the present study was to investigate the prognostic effect of involved and uninvolved HLC pairs and HLC ratios on progression in a series of patients with MGUS and SMM.Patients and MethodsAll specific serum HLC pairs were measured in 114 patients diagnosed with SMM (n = 27) and MGUS (n = 87) from 1983 to 2003. Also, the HLC ratios were calculated.ResultsProgression to symptomatic multiple myeloma was observed in 13 patients (8 with SMM and 5 with MGUS). The risk of progression was 6 times greater in those with SMM (P = .001) and 4 times greater for those with the IgA isotype (P = .01). The suppression of any IgM isotypes (IgMκ or IgMλ) in patients with IgA or IgG gammopathy or any IgA isotypes (IgAκ or IgAλ) in patients with IgG or IgM gammopathy was associated with a shorter time to progression to symptomatic gammopathy (P = .001 and P = .03, respectively). On multivariate analysis, the evolving pattern and suppression of any IgM HLC pair remained significant.ConclusionHLC ratios could be a valuable tool in the risk stratification of patients with SMM and MGUS, especially patients with IgG isotypes.