title: Comparison of serum free light chain and urine electrophoresis for the detection of the light chain component of monoclonal immunoglobulins in light chain and intact immunoglobulin multiple myeloma.
abstract: Response criteria for multiple myeloma are based upon changes in monoclonal protein levels quantified using serum and/or urine protein electrophoresis. The latter lacks sensitivity at low monoclonal protein levels and since 2001, the serum free light chain test has been available and its clinical utility proven, yet guidelines have not recommended it as a replacement for urine assessment. Herein we evaluated responses using serum free light chain measurements and serum and urine electrophoresis after 2 and 4 cycles of therapy and after stem cell transplantation in 25 light chain and 157 intact immunoglobulin myeloma patients enrolled in the IFM 2007-02 MM trial. All 25 light chain patients had measurable disease by serum free light chain and urine methods at presentation. By contrast 98 out of 157 intact immunoglobulin patients had measurable disease by serum free light chain compared to 55 out of 157 by urine electrophoresis. In all patients there was substantial agreement between predicate (serum/urine protein electrophoresis) and test (serum protein electrophoresis and serum free light chain) methods for response assessment (Weighted Kappa=0.83). Urine immunofixation became negative in 47% light chain and 43% intact immunoglobulin patients after 2 cycles of therapy. At this time the serum free light chain ratio normalised in only 11% and 27% patients, respectively. In summary we found good agreement between methods for response assessment, but the serum free light chain test provided greater sensitivity than urine electrophoresis for monitoring. To our knowledge this is the first report comparing both methods for response assignment based on the International Myeloma Working Group guidelines. (Clinical Trials Register.eu identifier: 2007-005204-40).
authors.affiliation: University Hospital Nantes, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dejoie
authors.affiliation: Institut Universitaire du Cancer, Toulouse, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Attal
authors.affiliation: University Hospital Nantes, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Moreau
authors.affiliation: Institut de Cancérologie de l'Ouest, Saint-Herblain, France.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Harousseau
authors.affiliation: Institut Universitaire du Cancer, University Hospital, CRCT, INSERM U1037, Toulouse, France avetloiseau.herve@iuct-oncopole.fr.
authors.forename: Herve
authors.initials: H
authors.lastname: Avet-Loiseau
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D054316:Biomarkers, Pharmacological / Q000097:blood / Q000652:urine; D000069286:Bortezomib / Q000627:therapeutic use; D003907:Dexamethasone / Q000627:therapeutic use; D004586:Electrophoresis; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007145:Immunoglobulin kappa-Chains / Q000097:blood* / Q000652:urine; D007146:Immunoglobulin lambda-Chains / Q000097:blood* / Q000652:urine; D008558:Melphalan / Q000627:therapeutic use; D009101:Multiple Myeloma / Q000097:blood / Q000175:diagnosis* / Q000276:immunology / Q000628:therapy*; D009391:Nephelometry and Turbidimetry; D017410:Practice Guidelines as Topic; D012189:Retrospective Studies; D013792:Thalidomide / Q000627:therapeutic use; D014184:Transplantation, Homologous
chemical_list: D054316:Biomarkers, Pharmacological; D007145:Immunoglobulin kappa-Chains; D007146:Immunoglobulin lambda-Chains; D013792:Thalidomide; D000069286:Bortezomib; D003907:Dexamethasone; D008558:Melphalan