Abstract
•The highest M−protein detection rates occur with MALDI-TOF MS plus FLC measurement.•MALDI-TOF MS can help accurately determine complete response status in patients.•Daratumumab can be distinguished from the M−protein in most samples by MALDI-TOF MS.•Relative concentration and mass difference matters for distinguishing proteins.
Daratumumab-based combination therapies have shown high rates of complete response (CR) and minimal residual disease negativity in patients with multiple myeloma. However, daratumumab, an IgGκ monoclonal antibody, interferes with electrophoretic techniques making it difficult to reliably define residual disease versus CR, especially in patients with IgGκ multiple myeloma.
Enrichment with polyclonal sheep antibody-coated magnetic microparticles combined with MALDI-TOF mass spectrometry (MALDI-TOF MS) analysis was used to detect M−proteins in serial samples from newly diagnosed multiple myeloma patients treated with daratumumab-based therapy. The performance of the MALDI-TOF MS assay was compared to that of a routine test panel (serum protein electrophoresis (SPEP), immunofixation (IFE) and serum free light chain (FLC)).
Comparison of MALDI-TOF MS to SPEP/IFE/FLC showed a concordance of 84.9% (p < 0.001). When MALDI-TOF MS and FLC results were combined, the M−protein detection rate was the same or better than the routine test panel. For the 9 patients who obtained CR during follow-up, MALDI-TOF MS detected an M−protein in 46% of subsequent samples. Daratumumab could be distinguished from the M−protein in 215/222 samples.
MALDI-TOF MS is useful in assessing CR in patients treated with monoclonal antibody-based therapies.
