Diagnostic and Treatment Approach for Multiple Myeloma with Negative Serum Paraprotein

Diagnostic Workup

The National Comprehensive Cancer Network recommends serum free light chain (FLC) assay with kappa/lambda ratio for detecting light chain myeloma when standard serum protein electrophoresis is negative 1
A 24-hour urine collection for total protein, urine protein electrophoresis (UPEP), and urine immunofixation electrophoresis (UIFE) is crucial to detect Bence Jones proteins (monoclonal free light chains) 1
Bone marrow aspiration and biopsy with immunohistochemistry and/or flow cytometry should be performed to confirm ≥10% clonal plasma cells 4
Complete blood count, serum creatinine, calcium, albumin, LDH, and beta-2 microglobulin should be assessed to evaluate for end-organ damage and staging 1
A full skeletal survey using X-ray, CT, or MRI should be performed to evaluate for lytic bone lesions 4

The International Myeloma Society recommends ≥10% clonal plasma cells on bone marrow examination or biopsy-proven plasmacytoma for diagnosis 4
An abnormal serum free light chain ratio with elevated involved light chain is a diagnostic criterion 2
Evidence of end-organ damage (CRAB criteria): hypercalcemia, renal insufficiency, anemia, or bone lesions is required for diagnosis 4

The European Society for Medical Oncology recommends a triple-agent induction regimen incorporating novel agents (bortezomib, lenalidomide, and dexamethasone) followed by autologous stem cell transplantation for transplant-eligible patients 5
The American Society of Clinical Oncology recommends high-dose melphalan 200 mg/m² as the preferred preparative regimen prior to transplantation 5

The National Comprehensive Cancer Network recommends long-term administration of bisphosphonates to reduce skeletal events 5
Full-dose aspirin is recommended with immunomodulator-based therapy 1
Therapeutic anticoagulation is recommended for those at high risk for thrombosis 1

The International Myeloma Society recommends assessment of response including serum free light chain measurements 2
Response criteria include stringent complete response (sCR), complete response (CR), very good partial response (VGPR), and partial response (PR) 2

The National Comprehensive Cancer Network recommends using the same test for serial measurements to ensure accurate relative quantification after quantifying the involved light chain 1
Serum FLC assay cannot completely replace 24-hour UPEP for monitoring patients with measurable urinary M-protein 2
FLC measurements can be affected by renal function, potentially leading to false elevations 2