Mass spectrometry

light chain. Although there is no difference in the way the various types of myeloma are treated, it’s important to know your type of heavy and light chain for monitoring purposes.

In addition to the immunoglobulin pair that your myeloma cells are making, you also have normal, intact immunoglobulin pairs circulating in your bloodstream. The Hevylite test can distinguish between the “involved” proteins – the heavy and light chain produced by the myeloma – and their “uninvolved” (i.e. normal) counterparts that have the same heavy chain isotype but are bound to a different light chain.

For example, if you have IgG kappa myeloma (the “involved” heavy and light chain), then your IgG lambda heavy and light chain pairs are the normal “uninvolved” immunoglobulins. Hevylite is an extremely sensitive measurement of both myeloma protein and normal immunoglobulins. It is an accurate way to measure IgA myeloma, which often does not show up by SPEP. When Hevylite reveals that normal Ig levels are suppressed, it can be an early indicator of relapse. Hevylite can detect extremely low levels of M-protein, indicating the presence of minimal residual disease (MRD).

Mass spectrometry (“mass spec”) is a highly sensitive new method to detect and measure the precise amount of the myeloma monoclonal protein in the blood. It is much more sensitive and accurate than SPEP along with IFE. Mass spec can be used for the diagnosis and monitoring of MGUS, SMM, and active myeloma. Mass spec is a simple blood test, but it is still not broadly available. Wider use of mass spec is expected in 2022. In February 2021, Blood Cancer Journal published a report by the International Myeloma Working Group (IMWG) Mass Spectrometry Committee on the benefits of mass spec methods in diagnosing and monitoring patients with myeloma and related disorders. Mass spec can distinguish between very low levels of myeloma protein and blood levels of monoclonal antibodies used to treat myeloma. Making this distinction can confirm if the patient has achieved CR. In June 2021, two abstracts presented at the ASCO annual meeting evaluated the emerging role of mass spec: the STaMINA clinical trial demonstrated that the non-invasive “MASS-FIX” method of predicting outcomes is equivalent to bone marrow MRD next-generation flow (NGF) testing, and the GEM clinical trial demonstrated that the results of bone marrow MRD NGF were consistent with the serial mass spec results.