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. 2022 Nov 30:12:1056293.
doi: 10.3389/fonc.2022.1056293. eCollection 2022.

Can urine studies be replaced by serum free light chains measurements to assign responses in multiple myeloma patients?

Maria Cruz Cárdenas  1 , Belén Iñigo  2 , Isabel Ortega  1 , Maria Angeles Palomar  1 , Marina Menéndez  2 , Paula Plaza  1 , Mercedes Martínez-Novillo  1 , Celina Benavente  2
Affiliations

Can urine studies be replaced by serum free light chains measurements to assign responses in multiple myeloma patients?

Maria Cruz Cárdenas et al. Front Oncol. .

Abstract

Serum and urine protein electrophoresis and immunofixation are the preferred techniques for monitoring monoclonal proteins and evaluating treatment response in multiple myeloma (MM) patients with measurable disease. However, urine studies are subjected to limitations that may lead to inaccuracies or prevent guidelines compliance. We retrospectively studied if the substitution of urine studies by measuring serum free light chains (sFLCs) results in a comparable disease monitoring, both in intact immunoglobulin (II) and light chain (LC) MM patients. In our cohort, equal or higher percentages of disease were identified by sFLCs at baseline and maximum response as compared to urine studies. Achieving very good partial response or better (≥VGPR) according to the response criteria proposed by the French group (evaluating sFLCs instead of urine) and the IMWG response criteria were associated to a 62% and 63% reduced risk of progression, respectively. A similar prognostic value for reaching ≥VGPR was also observed among LCMM patients when the French group and the IMWG response criteria were applied. Overall, these results support the replacement of urine studies by the sFLCs assay in IIMM. In LCMM, sFLCs could be used for monitoring and urine studies could be performed only to confirm complete remissions and progressions.

Keywords: multiple myeloma; response criteria; serum free light chains; urine protein electrophoresis; urine protein immunofixation.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Percentage of detectable and measurable disease by SPEP/sIFE, serum FLCs and UPEP/uIFE tests for both, the entire cohort and LCMM patients (A) before starting the first and/or the second line of treatment (baseline) and (B) at time of maximum response. LCMM, light chain multiple myeloma; sFLCr, serum free light chains ratio; sIFE, serum immunofixation electrophoresis; SPEP, serum protein electrophoresis; uIFE, urine immunofixation electrophoresis; UPEP, urine protein electrophoresis.
Figure 2
Figure 2
Progression-free survival (PFS) according to the normalized sFLCr and negativized 24-hour urine studies at maximum response for the entire patient cohort (A) and for LCMM patients (B). mPFS, median progression-free survival; HR, Hazard ratio; sFLCr, serum free light chains ratio; uIFE, urine immunofixation electrophoresis; UPEP, urine protein electrophoresis.
Figure 3
Figure 3
Progression-free survival (PFS) according to the depth of response (≥VGPR or (A) the entire cohort and (B) only in LCMM patients. HR, Hazard ratio; IMWG, International Myeloma Working Group; mPFS, median progression-free survival; VGPR, very good partial response.
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