Table 1 Techniques to measure response... | American Society of Hematology

Table 1

Techniques to measure response to treatment in multiple myeloma

	Comments
Currently used techniques
Bone marrow aspiration	Easy Inexpensive Painful (requires local anesthesia) Not always performed in multicenter studies Plasma cell infiltration often underestimated (blood dilution, heterogeneous involvement)
Bone marrow biopsy	Easy Inexpensive Painful (requires local anesthesia/analgesia) Necessary if bone marrow aspiration fails
Serum/24-h urine electrophoresis (agarose gel or capillary zone)	Easy Inexpensive Lowest detected level of M-component: 0.2-0.6 g/L 24-h urine collection not always complete
Immunofixation (serum/urine)	Easy More expensive than electrophoresis Not quantitative Lowest detected level of M-component: 0.12–0.25 g/L
Serum free light chain assay (and k/λ ratio)	More expensive than immunofixation Necessary for response assessment in oligo/nonsecretory myeloma Useful in light-chain myeloma (but no correlation between FLC and urine electrophoresis) Necessary for defining stringent CR
Techniques under evaluation
Imaging techniques (MRI, PET scan)	Expensive PET scan not available everywhere May detect nonsecretory tumor masses
Bone marrow immunochemistry/fluorescence	Detects monoclonal plasma cells Necessary for defining stringent CR More expensive than bone marrow cytology/histology
Bone marrow immunophenotyping (multiparameter flow cytometry)	Expensive Highly sensitive (10⁻⁴) Requires specialized labs (not validated at the multicenter level)
Bone marrow molecular remission assessment (allelic-specific oligonucleotide RQ-PCR)	The most sensitive technique (up to 10⁻⁶) Expensive and cumbersome Available at a limited number of specialized centers

	Comments
Currently used techniques
Bone marrow aspiration	Easy Inexpensive Painful (requires local anesthesia) Not always performed in multicenter studies Plasma cell infiltration often underestimated (blood dilution, heterogeneous involvement)
Bone marrow biopsy	Easy Inexpensive Painful (requires local anesthesia/analgesia) Necessary if bone marrow aspiration fails
Serum/24-h urine electrophoresis (agarose gel or capillary zone)	Easy Inexpensive Lowest detected level of M-component: 0.2-0.6 g/L 24-h urine collection not always complete
Immunofixation (serum/urine)	Easy More expensive than electrophoresis Not quantitative Lowest detected level of M-component: 0.12–0.25 g/L
Serum free light chain assay (and k/λ ratio)	More expensive than immunofixation Necessary for response assessment in oligo/nonsecretory myeloma Useful in light-chain myeloma (but no correlation between FLC and urine electrophoresis) Necessary for defining stringent CR
Techniques under evaluation
Imaging techniques (MRI, PET scan)	Expensive PET scan not available everywhere May detect nonsecretory tumor masses
Bone marrow immunochemistry/fluorescence	Detects monoclonal plasma cells Necessary for defining stringent CR More expensive than bone marrow cytology/histology
Bone marrow immunophenotyping (multiparameter flow cytometry)	Expensive Highly sensitive (10⁻⁴) Requires specialized labs (not validated at the multicenter level)
Bone marrow molecular remission assessment (allelic-specific oligonucleotide RQ-PCR)	The most sensitive technique (up to 10⁻⁶) Expensive and cumbersome Available at a limited number of specialized centers

MRI indicates magnetic resonance imaging; PET, positron emission tomography; RQ-PCR, real-time quantitative–polymerase chain reaction.