Interference of Daratumumab Treatment in the Biological Monitoring of Multiple Myeloma

BACKGROUND: Multiple myeloma is a plasma cell malignancy characterized by monoclonal immunoglobulin production. Daratumumab has improved therapeutic outcomes but can interfere with laboratory assessments. METHODS: A 73-year-old woman with IgG kappa multiple myeloma achieved remission after initial treatment, then relapsed and received DRD. A monoclonal IgG kappa spike was observed on follow-up SPEP and IFE. RESULTS: Daratumumab, due to its IgG1 kappa structure, may mimic disease-related monoclonal proteins, potentially leading to false detection of residual disease and misclassification of complete response as very good partial response. CONCLUSIONS: Recognizing such interference and ensuring strong clinician-biologist collaboration is essential for accurate response interpretation.