Clark, Raynell

Abstract Background: The serum free light chain (FLC) ratio is a readily available laboratory test that has independent prognostic significance in monoclonal gammopathy of undetermined significance (MGUS) (Blood2005;106:812–17) and solitary plasmacytoma (Blood2006;108:1979–83). The purpose of this study was to determine if the FLC ratio will be of prognostic value in multiple myeloma (MM). Methods: We used a well characterized cohort of 1027 newly diagnosed MM patients seen at Mayo Clinic from January 1, 1985 to December 31, 1998 (Mayo Clin Proc2003;78:21–33) to ensure adequate follow up. Archived serum samples from blood drawn within 30 days of initial diagnosis were available on 790 of the 1027 patients. Quantitation of serum free κ and λ concentrations was performed on the archived sera by immunonephelometry, using specific antibodies on a BNII nephelometer. FLC ratio was calculated as κ /λ, i.e., free κ concentration divided by free λ, reference range 0.26–1.65. If the FLC ratio is >1.65, κ is considered to be the “involved” FLC and λ the “uninvolved” FLC, and vice versa if the ratio is less than 0.26. Incorporation of FLC into the International Staging System (ISS) was assessed in 576 of 790 patients (73%), in whom samples or data were available to estimate the ISS. Results: 790 patients (median age 66 years) were studied. The FLC ratio was outside the reference range in 95.1% of patients. The median involved κ and λ concentrations were 37.1 and 71.3 mg/dL, respectively. A cut-point κ /λ FLC ratio of <0.03 or >32 was chosen for further modeling analysis on the basis of its separation of the cohort into two roughly comparable parts. Overall survival was significantly inferior in patients with an FLC ratio <0.03 or >32 (n=479 patients) compared to those with an FLC ratio that was 0.03–32 (n=311 patients), with median survival of 30 versus 39 months, respectively, P<0.001 (hazard ratio 1.3, 95% CI 1.12–1.54). The FLC ratio (<0.03 or >32) retained independent significance after adjusting for the International Staging System (ISS) (P=0.03). The FLC ratio made the most significant contribution to predicting prognosis in patients with ISS Stage 2 (n=265 pts), separating this category of patients into those with 5 year survival rates of 20.5% (FLC ratio <0.03 or >32; n=152 pts) versus 35.2% (FLC ratio 0.03–32; n=113 pts), P=0.02. We studied the additional prognostic value of the serum FLC to the variables used in the ISS by defining FLC ratio <0.03 or >32, Sβ2M ≥3.5 g/L, and serum albumin <3.5 g/dL as three risk factors in a risk-stratification model. Patients with 0, 1, 2, or 3 risk factors had significantly different overall survival, with median overall survival times of 51, 39, 30 and 22 months, respectively, P<0.001. Conclusions: The serum FLC ratio at initial diagnosis is an important predictor of prognosis in myeloma. We show that the serum FLC ratio can be incorporated into the ISS, providing the greatest prognostic value in ISS Stage 2 patients, as well as providing a new risk-stratification model.

Abstract Abstract 1788 Poster Board I-814 Background Clinically available prognostic factors for progression of MGUS to myeloma include the size of the M-spike, heavy chain isotype, and free light chain (FLC) K/L ratio. The combined use of these variables provides approximately a 10-fold difference in risk for progression. The highest risk group, however, still has only a 27% twenty year risk of progression. Therefore, additional predictors of progression are needed. Suppression of uninvolved immunoglobulins has been an inconsistent predictor of progression. The novel Hevylite” assay measures concentrations of each isotype-specific immunoglobulin heavy light chain (HLC) pair (i.e., IgG kappa, IgG lambda, IgA kappa, IgA lambda) and enables us for the first time to determine if suppression of isotype-specific Ig of the opposite HLC is occurring and if it is predictive of progression of MGUS to myeloma. We studied the prognostic value of isotype specific HLC suppression of uninvolved immunoglobins as a predictor of progression in MGUS. Methods: Total immunoglobulins were quantitated by immunonephelometry, and suppression was defined as concentrations less than the lower limit of the reference range. HLC concentrations were quantitated with Hevylite reagents (The Binding Site, Ltd). The antibodies used in this investigational nephelometric assay span epitopes in the junctional areas between the HLC constant regions. Based on reference ranges for GK (407-1130 mg/dL), GL (188-583 mg/dL), AK (55-292 mg/dL), and AL (39-249 mg/dL) that we derived from 276 normal samples, we compared the proportion of patients who had isotype specific suppression of the opposite HLC pair among 30 patients with MGUS who progressed to myeloma versus 36 patients who had not progressed over a similar follow-up period. To confirm the relationship of isotype specific HLC pair suppression compared to suppression of uninvolved immunoglobulins of other heavy chain classes, we tested a second cohort of stored samples from 50 IgG and 14 IgA MGUS patients prior to the development of MM. Results In the initial samples from 36 IgG MGUS patients who had stable disease, 6% had suppression of uninvolved intact immunoglobulins of IgA and/or IgM, while 22% had isotype specific suppression of the opposite HLC pair (i.e., IgG lambda suppressed in IgG kappa MGUS, and vice versa). In contrast, in baseline samples from 30 IgG MGUS patients who eventually progressed to myeloma or related malignancy, 7% had suppression of IgA and/or IgM, while 40% had isotype specific suppression of the opposite IgG HLC pair. Thus, HLC pair suppression was more frequent than suppression of Igs from other heavy chain classes, and MGUS patients who eventually progressed had a 2-fold higher rate of isotype specific HLC pair suppression than stable MGUS patients. These findings were confirmed independently on a second cohort of patients who progressed to myeloma 5-10 years after blood collection. In samples from 50 IgG MGUS patients, 42% had suppression of Igs of other heavy chain classes, while 80% had suppression of the isotype specific HLC by the Hevylite assay. In the last samples prior to progression, the suppression of heavy chain classes increased to 60%, while isotype specific HLC suppression rose to 90%. Interestingly, the 14 IgA patients had equivalent suppression of gamma or mu heavy chain classes as compared to the HLC pairs, with 50% of the patients having suppression in the initial sample and 79% in the last sample prior to MM. Conclusion Our data suggest that suppression of the opposite IgG HLC pair is a predictor of patients destined for progression. Isotype specific HLC pair suppression of this nature is more frequent in these patients (more sensitive) than suppression of other heavy chain classes. We were not able to demonstrate a similar effect in IgA MGUS. Larger studies are underway to determine if HLC pair suppression is independent of M-spike quantitation, heavy chain isotype, and FLC ratio. Biologically, our findings suggest that clonal IgG plasma cells are able to suppress other IgG producing non-clonal plasma cells far more effectively than IgA or IgM secreting cells, and this occurs more frequently with cells that will eventually undergo malignant transformation. Disclosures Bradwell: The Binding Site Group Ltd: Equity Ownership.

Abstract Immunoglobulin free light chains (FLCs) are the precursors of amyloid fibrils in primary amyloidosis (AL). We studied the relationship between FLC levels and clinical features in 730 patients with newly diagnosed AL. The plasma cell clone was λ in 72% patients, and κ in 28% patients. κ-AL had more GI tract and liver involvement, where as renal involvement was more with λ-AL. While the overall survival (OS) was similar for κ and λ-AL, the median OS for those without an identifiable serum heavy chain was significantly shorter (12.6 vs 29.9 months; P = .02). The OS was shorter among those with a higher dFLC (involved FLC−uninvolved FLC; κ > 29.4 mg/dL or λ > 18.2 mg/dL using median for cutoff); 10.9 vs 37.1 months; P < .001. In multivariate analysis, dFLC was independent of other prognostic factors. The type of light chain impacts the spectrum of organ involvement and the FLC burden correlates with survival in AL.

Monoclonal gammopathy of undetermined significance (MGUS) is a premalignant plasma-cell proliferative disorder associated with a life-long risk of progression to multiple myeloma (MM). It is not known whether MM is always preceded by a premalignant asymptomatic MGUS stage. Among 77 469 healthy adults enrolled in the nationwide population-based prospective Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, we identified 71 subjects who developed MM during the course of the study in whom serially collected (up to 6) prediagnostic serum samples obtained 2 to 9.8 years prior to MM diagnosis were available. Using assays for monoclonal (M)–proteins (electrophoresis/immunofixation) and kappa-lambda free light chains (FLCs), we determined longitudinally the prevalence of MGUS and characterized patterns of monoclonal immunoglobulin abnormalities prior to MM diagnosis. MGUS was present in 100.0% (87.2%-100.0%), 98.3% (90.8%-100.0%), 97.9% (88.9%-100.0%), 94.6% (81.8%-99.3%), 100.0% (86.3%-100.0%), 93.3% (68.1%-99.8%), and 82.4% (56.6%-96.2%) at 2, 3, 4, 5, 6, 7, and 8+ years prior to MM diagnosis, respectively. In approximately half the study population, the M-protein concentration and involved FLC-ratio levels showed a yearly increase prior to MM diagnosis. In the present study, an asymptomatic MGUS stage consistently preceded MM. Novel molecular markers are needed to better predict progression to MM in patients with MGUS.

We hypothesized that increased monoclonal free kappa or lambda immunoglobulin light chains in smoldering multiple myeloma (SMM), as detected by the serum free light chain (FLC) assay, indicates an increased risk of progression to active myeloma. Baseline serum samples obtained within 30 days of diagnosis were available in 273 patients with SMM seen from 1970 to 1995. At a median follow-up of surviving patients of 12.4 years, transformation to active disease has occurred in 59%. The best breakpoint for predicting risk of progression was an FLC ratio of 0.125 or less, or 8 or more (hazard ratio, 2.3; 95% CI, 1.6-3.2). The extent of abnormality of FLC ratio was independent of SMM risk categories defined by number of bone marrow plasma cells (BMPCs) and size of serum M proteins (BMPC ≥ 10% and serum M protein ≥ 3 g/dL; BMPC ≥ 10% but serum M protein < 3 g/dL; and serum M protein≥ 3 g/dL but BMPC < 10%). Incorporating the FLC ratio into the risk model, the 5-year progression rates in high-, intermediate-, and low-risk groups were 76%, 51%, and 25%, respectively. The serum immunoglobulin FLC ratio is an important additional determinant of clinical outcome in patients with SMM.

AbstractThe immunoglobulin free light chain (FLC) is the precursor protein of amyloid in primary systemic amyloidosis (AL). Historically, the ability to monitor the amyloid protein precursor protein has been crude. We evaluated the utility of the FLC assay in a retrospective analysis of patients with AL undergoing peripheral blood stem cell transplantation (PBSCT). Ninety-three such patients had serial FLC measurements performed. The prognostic effects of the initial concentration and the extent of reduction of monoclonal FLC on survival were studied. There was a significantly higher risk of death in patients with higher baseline FLC (hazard ratio 2.6, P < .04). Baseline FLC correlated with serum cardiac troponin levels, and higher FLC levels were associated with more organs involved by amyloid, suggesting that high FLC levels may be associated with more advanced disease. The percent FLC reduction did not predict for survival, but the absolute level of FLC achieved after therapy did. Normalization of FLC level after PBSCT predicted for both organ response and complete hematologic response. Achievement of FLC response was a better predictor of survival than achievement of complete hematologic response or normalization of the FLC ratio. FLC measurements both before and after PBSCT are important predictors of patient outcome.

Abstract We hypothesized that the presence of monoclonal free kappa or lambda immunoglobulin light chains in monoclonal gammopathy of undetermined significance (MGUS), as detected by the serum free light chain (FLC) assay increases the risk of progression to malignancy. Of 1384 patients with MGUS from Southeastern Minnesota seen at the Mayo Clinic from 1960 to 1994, baseline serum samples obtained within 30 days of diagnosis were available in 1148. At a median follow-up of 15 years, malignant progression had occurred in 87 (7.6%) patients. An abnormal FLC ratio (kappa-lambda ratio &lt; 0.26 or &gt; 1.65) was detected in 379 (33%) patients. The risk of progression in patients with an abnormal FLC ratio was significantly higher compared with patients with a normal ratio (hazard ratio, 3.5; 95% confidence interval [CI], 2.3-5.5; P &lt; .001) and was independent of the size and type of the serum monoclonal (M) protein. Patients with an abnormal serum FLC ratio, non–immunoglobulin G (non-IgG) MGUS, and a high serum M protein level (≥ 15 g/L) had a risk of progression at 20 years of 58% (high-risk MGUS) versus 37% with any 2 of these risk factors (high-intermediate risk), 21% with one risk factor (low-intermediate risk), and 5% when none of the risk factors were present (low risk).