title: Appraisal of immunoglobulin free light chain as a marker of response.
abstract: The immunoglobulin free light chain (FLC) assay is an invaluable tool for following patients with oligosecretory plasma cell dyscrasia. Baseline values have also been shown to be prognostic in all plasma cell disorders tested. A looming question, however, is the role it should play in following myeloma patients with disease that is measurable using serum and urine electrophoresis. We used the data and stored samples from a mature Eastern Cooperative Oncology Group clinical trial (E9486) to assess serum levels of FLC at baseline and after 2 months of alkylator-based therapy. For serial determinations, the absolute level of involved serum FLC or the difference of the involved and uninvolved FLC is preferred over the ratio of involved to uninvolved FLC. FLC response after 2 months of therapy was superior to early M-protein measurement to predict overall response. The ideal cut-point for FLC change appears to be between 40% and 50% reduction. The correlation between serial measurements of serum FLC and urine M-protein is inadequate to abolish the serial 24-hour urine protein. Although baseline values of FLC are prognostic in newly diagnosed myeloma patients, serial measurements do not appear to have added value in patients who have M-proteins measurable by electrophoresis.
authors: Departments of Hematology, Mayo Clinic, Rochester, MN, USA. dispenzieri.angela@mayo.edu
authors: Angela
authors: A
authors: Dispenzieri
authors: Lijun
authors: L
authors: Zhang
authors: Jerry A
authors: JA
authors: Katzmann
authors: Melissa
authors: M
authors: Snyder
authors: Emily
authors: E
authors: Blood
authors: Roberta
authors: R
authors: Degoey
authors: Kimberly
authors: K
authors: Henderson
authors: Robert A
authors: RA
authors: Kyle
authors: Martin M
authors: MM
authors: Oken
authors: Arthur R
authors: AR
authors: Bradwell
authors: Philip R
authors: PR
authors: Greipp
mesh_terms: D015415:Biomarkers / Q000097:blood; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood*; D009101:Multiple Myeloma / Q000175:diagnosis*; D011379:Prognosis; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers; D007147:Immunoglobulin Light Chains