Evaluating the heavy/light chain immunoglobulin biomarker for early relapse detection in multiple myeloma: A comparative study with conventional methods

The objective of this study is to evaluate the use of the immunoglobulin heavy/light chain biomarker in the early detection of biochemical relapse in patients with multiple myeloma under treatment. The immunoglobulin heavy/light chain is a test that measures the heavy chain/light chain pair of each immunoglobulin isotype, allowing for the calculation of the immunoglobulin ratios of IgGκ/IgGλ, IgAκ/IgAλ and IgMκ/IgMλ, which can be used as surrogate markers of monoclonal proliferation processes. For the study, 80 samples were selected from 40 patients with multiple myeloma, who showed evidence of biochemical relapse in the past 5 years, corresponding to two samples per patient. Heavy/light chain pairs of the monoclonal isotype were determined in the sample that showed biochemical relapse and in the previous follow-up sample. Results were compared with those from serum immunofixation, serum protein electrophoresis, and free light chains. Within the samples before biochemical relapse, which had negative serum electrophoresis and immunofixation, 18% had an abnormal heavy/light chain ratio, 33% had an abnormal free light chain ratio, and 40% had at least one of these ratios altered. At the moment of biochemical relapse, i.e., samples with positive immunofixation, 43% had positive serum protein electrophoresis, 43% had an abnormal heavy/light chain ratio, 58% had an abnormal free light chain ratio, and 68% had at least one abnormal ratio. The assessment of heavy/light chains and free light chains may have a beneficial impact on the early detection of biochemical relapse in patients with multiple myeloma, particularly in IgA-type MM, potentially eliminating the need for serum electrophoresis.