[Serum free light chains for diagnosis and follow-up of multiple myeloma].
BACKGROUND
Free light chain (FLC) is widely used to evaluate B-cell proliferative diseases. Herein, we estimated the clinical usefulness of serum FLC in multiple myeloma (MM).


METHODS
Fifty-one patients were enrolled. We performed FLC analysis, protein electrophoresis (PEP), and immunofixation electrophoresis (IFE). FLC was measured using Toshiba 200 FR Neo with FREELITE, and kappa/lambda (kappa/lambda) ratio was calculated. We compared these parameters in 41 patients with increased FLC before and after bortezomib treatment. Complete response (CR) was defined as the disappearance of monoclonal (M) protein in serum and/or urine as measured by IFE. Partial response (PR) was defined as >or=50% reduction of serum M protein. Early objective response (EOR) included both CR and PR. Minimal response (MR) was defined as 25-49% reduction of M protein and stable disease (SD) as <25% reduction.


RESULTS
Forty-one (80.4%) of the 51 patients studied revealed increment of FLC and the five patients with no increment revealed an abnormal kappa/lambda ratio. Especially, all of the light chain myeloma and non-secretory myeloma showed increased FLC concentrations. Among the patients with EOR, 72.4% (21/29) showed a normal or subnormal FLC concentration after the first cycle of treatment. Otherwise, PEP and IFE normalized in 24.1% (7/29) and 24.1% (7/29), respectively. The ratio of decreased FLC after the first cycle of treatment was significantly different between EOR and other response groups (MR, SD) (90.6% vs 51.8%, P=0.011).


CONCLUSIONS
FLC was considered as a good diagnostic method in complement with PEP and IFE in MM, especially in light chain myeloma or non-secretory myeloma. Moreover, FLC is a useful monitoring tool because it reflects therapy results more rapidly owing to a short serum half-life.
Jung
Seonkyung
S
Department of Laboratory Medicine, The Catholic University of Korea, Seoul, Korea.
Kim
Myungshin
M
Lim
Jihyang
J
Kim
Yonggoo
Y
Han
Kyungja
K
Min
Chang-Kee
CK
Min
Woo-Sung
WS
D000328:Adult; D000368:Aged; D001897:Boronic Acids / Q000627:therapeutic use; D000069286:Bortezomib; D005260:Female; D006801:Humans; D007122:Immunoelectrophoresis; D007147:Immunoglobulin Light Chains / Q000097:blood* / Q000652:urine; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000175:diagnosis* / Q000628:therapy; D011719:Pyrazines / Q000627:therapeutic use; D011933:Reagent Kits, Diagnostic
D001897:Boronic Acids; D007147:Immunoglobulin Light Chains; D011719:Pyrazines; D011933:Reagent Kits, Diagnostic; D000069286:Bortezomib