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Multiple Myeloma, Gammopathies

Utility of serum free light chain measurements in multiple myeloma patients not achieving complete response to therapy



Normalization of the serum-free light-chain ratio (FLCr) with the absence of bone marrow monoclonal plasma cells following achievement of a complete response (CR) to therapy denotes a stringent CR in multiple myeloma (MM), and is associated with improved overall survival (OS). However, its value in patients achieving <CR is not clear. We hypothesized that patients achieving a normalization of FLCr with initial therapy of MM will have an improved outcome, even in the absence of a CR. We retrospectively evaluated 449 patients with newly diagnosed MM with measurable disease at baseline, who did not achieve a CR with initial therapy. One hundred and fifty-three patients (34%) had a normal FLCr, whereas 296 (66%) had an abnormal ratio. Patients with a normal FLCr had a longer progression-free survival (29 vs 16 months, P<0.001) and OS (91 vs 58 months, P<0.001). Normalization of FLCr retained its prognostic value in a multivariable model. Our results suggest an important role for sFLC measurement in disease monitoring even in patients who achieve only a partial response to therapy. Obtaining a normal FLCr confers a favorable prognosis independent from other factors, supporting the inclusion of sFLC in all levels of response criteria.

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This publication was made possible by CTSA Grant Number UL1 TR000135 from the National Center for Advancing Translational Sciences, a component of the National Institutes of Health (NIH). MA is supported by the Gene and Mary-Lou Kurtz fellowship in myeloma. We also would like to acknowledge Colin Colby and Dirk Larson for their help with database management and patient identification for the study. This work was supported in part by the Mayo Clinic Hematological Malignancies Program, R01 CA168762-03 (SKK and SVR), R01CA 107476-11 (SKK and SVR) and R01CA 167511-2 (SKK).

Author Contributions

MA and SKK designed the study, extracted the data, performed the analysis and wrote the manuscript. SVR, AD, MAG, MQL, FKB, YLH, DD, PK, SRH, JAL and RAK provided patients and critically reviewed and edited the manuscript.


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Correspondence to S K Kumar.

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Alhaj Moustafa, M., Rajkumar, S., Dispenzieri, A. et al. Utility of serum free light chain measurements in multiple myeloma patients not achieving complete response to therapy. Leukemia 29, 2033–2038 (2015).

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