Kyle, Robert A.

Abstract Abstract 934 Background: An increased risk of developing myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) has been observed for over 40 years in patients with multiple myeloma (MM). While treatment for MM has been implicated as the cause of excess MDS/AML, the risk may also be related to the underlying plasma cell proliferative disease process or an inherent predisposition to other hematologic malignancies in patients with plasma cell disorders. A recent study found an increased risk of AML/MDS for patients with monoclonal gammopathy of undetermined significance (MGUS) where there is no confounding chemotherapy effect to consider (Mailankody S, Blood2011; 118:4086-92). However, that report is subject to detection bias (i.e. association is related to reason for electrophoretic testing rather than the result of the test) since the population was not uniformly screened for MGUS. The purpose of this study was to determine if there was an increased risk of AML/MDS and other acute leukemias in persons with MGUS in a large population-based cohort systematically screened for the presence or absence of MGUS. Methods: The study utilized the population-based cohort established to estimate the prevalence of MGUS in the general population (N Engl J Med 2006; 354:1362-9). Serum samples were collected from 21,463 of the 28,038 residents of Olmsted County, Minnesota age 50 years or older as of 1/1/1995. Serum electrophoresis and immunofixation were used to determine MGUS status by testing all serum samples for the presence of a monoclonal protein. MGUS status was then linked to diagnoses entered in the Mayo Clinic Medical Index from 1/1/1975 to last follow up or 5/31/2006. For any patient in whom the diagnosis of AML/MDS or acute lymphoblastic leukemia (ALL) was in doubt, the diagnosis was verified by medical record review. For MGUS patients who progressed to MM or related disorder, only diagnosis of leukemia made prior to progression was considered. Results: 17,315 patients who consented to serum analysis were included in this study; blinded patients included in the original cohort could not be evaluated. The final study cohort represents 435,021 person-years of follow-up. Mean follow up for patients with MGUS (n=605) was 24.64 years (range 0.11–30.57); controls (n=16,710) had a mean follow up of 25.14 years (range 0.01–31.40). MGUS patients had a significantly higher risk of developing acute leukemia (AML/ALL) or MDS compared to controls, risk ratio 2.20 (95% CI 1.23–3.92), p=0.008 (see Table). There was a higher risk of developing AML/MDS compared to controls, risk ratio 1.80 (95% CI .09-3.59), p=0.09. The risk of developing MDS was statistically significant (RR=2.10, p=0.049). MGUS patients had a 4.18-fold increased risk of developing ALL (p=0.010) and a 2.35-fold increased risk of developing any acute leukemia (p=0.050) over the general population. In subset analysis, patients with IgA/IgG MGUS had a 1.99-fold increased risk of developing MDS (p=0.108), while patients with an IgM M spike had a 2.81-fold increased risk of developing MDS over controls (p=0.152). Though MDS was observed in patients with IgA, IgG, and IgM M-spikes, AML was only observed only in patients with IgA or IgG isotypes (n=2/484). Conclusion: Our population-based study suggests MGUS is associated with a 1.8-fold increased risk of developing MDS/AML over the general population. The risk of AML/MDS is more modest than the 8-fold increased risk suggested in a previous report (Mailankody S, Blood2011; 118:4086-92). The smaller risk ratios in our study are likely related to our population-based cohort design that uniformly screened for the presence or absence of MGUS, and thereby minimized any amplification of risk that can occur in the presence of ascertainment bias. We also found a significant increase in the risk of ALL in persons with MGUS that requires further study. Our study supports the hypothesis that there may be an inherent increased risk of acute leukemia and MDS in patients with plasma cell disorders that is independent of myeloma therapy. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 3972 Background: The treatment paradigm for myeloma has undergone a dramatic shift in the past decade with the introduction of the novel agents and their application at every stage of the treatment. We and others had previously shown that survival of patients with myeloma had improved in the earlier half of the last decade and attributed this to a combination of novel therapies as well as increased use of stem cell transplant. It is not clear if this momentum in improving survival has been maintained. We examined the survival trends of patients with newly diagnosed myeloma seen within the past decade to examine this question. Patients and Methods: We studied 1056 patients with newly diagnosed myeloma, who were seen at Mayo Clinic between January 1, 2001 and December 31, 2010; who were seen within 30 days of their diagnosis. For examination of the time trends, we grouped the time interval into two five year periods, 2001–2005 and 2006–2010. Survival was estimated using Kaplan Meier method and survival curves were compared by log rank test. Impact of various prognostic factors was evaluated using Cox proportional hazards test. Results: The median age at diagnosis was 65 (range; 22–92), and 59% were male. The median estimated follow up for the entire cohort was 4.6 years (95% CI; 4.4, 4.9) and 57% of the patients were alive at last follow up. The median overall survival (OS) for the entire cohort was 5.4 years (95% CI; 5, 6.3). The overall survival for patients in the 2001–2005 group was 4.6 years compared with not reached for the 2006–2010 cohort (P< 0.001). The five-year estimated OS was 48% for the earlier group compared with 66% for the latter group. The estimated 1-year survival was 90% for the recent cohort compared with 83% for the earlier cohort, suggesting improvements in the early mortality. Interestingly, the improvement was predominantly seen in the older age group (>65 years; 49%). The 5-year survival of the older patients improved significantly from 31% (2001–2005) to 56% (2006–2010) (P<0.001). In contrast, among younger patients (≤65 years of age), the 5-year survival improved only marginally from 63% (2001–2005) to 73% (2006–2010) (P=NS). One or more novel agents (Lenalidomide, thalidomide or bortezomib) were used as part of initial therapy in 631 (62% of 1021 in whom treatment data was available). The OS among of this group was 7.3 years (95% CI; 5.9, NR) compared with 3.8 years (95% CI; 3.1, 4.6). In a multivariate model that included both use of novel agent and the year group, only the novel agent use was associated with improved survival suggesting that the improvement in the survival is related to the increased use of novel agents in the initial therapy. No significant differences were observed between the groups in terms of conventional prognostic factors. Conclusions: The current results confirm continued improvement in the overall survival of patients, even within the last 10 year period, and highlight the impact of initial therapy with novel agents. Most importantly, we demonstrate that the improved survival has primarily benefited older patients. Our study highlights that urgent need for additional new agents to provide further survival improvement for younger patients, and in order achieve a cure for this disease. Disclosures: Kumar: Merck: Consultancy, Honoraria; Celgene: Research Funding; Millennium: Research Funding; Novartis: Research Funding; Cephalon: Research Funding; Genzyme: Research Funding. Dispenzieri:Celgene: Research Funding; Millennium Pharmaceuticals, Inc.: Research Funding; Janssen Research & Development: Research Funding. Gertz:Binding Site: Honoraria.

Abstract Abstract 2059 Introduction: Two randomized trials have demonstrated a benefit in progression free survival (PFS) of 18–20 mofor maintenance treatment with lenalidomide after auto-PBSCT for multiple myeloma (MM). Although results on survival benefit are conflicting and quality of life (QOL) data is lacking, some have begun to recommend maintenance. No study has evaluated patient perceptions of maintenance. We conducted a systematic survey of MM patients (pts) regarding what constitutes a meaningful benefit that would make burdens of maintenance (toxicity and cost) acceptable. Methods: We mailed a brief self-administered survey in 3 waves to 1159 consecutive living pts evaluated at Mayo Clinic. The survey provided background on the standard of care for MM in transplant eligible pts and data on maintenance. Pts were asked to estimate the magnitude of OS benefit that would be acceptable for varying degrees of toxicity and cost. Results: Of the 1159 surveys sent, 886 pts (83.2%) responded, including 150 notifying us of a decision not to participate. 736 pts returned a completed survey (66% raw response rate). (56%) male, 407 (55%) had undergone auto-PBSCT, 467 (63%) had discussed maintenance with a physician, and 9 (1%) pts had received no treatment. 10% of pts had MM for 3–12 mo, 14% for 1–2 yr, 13% for 2–3 yr, 20% for 3–5 yr, 44% for 5 yr or more. Pt age: 4% 18–49 yr, 24% 50–59 yr, 40% 60–69 yr, 27% 70–79 yr, and 6% >80 yrs. The most worrisome potential toxicity was identified as peripheral neuropathy by 27% of pts, cytopenias by 24%, LE DVT 20%, fatigue 15%, nausea 8%, diarrhea/constipation 7%. In response to a question about whether they would choose maintenance if there was a PFS benefit but no improvement in OS, 92% would opt for maintenance if it were known to cause mild toxicity, while 77% would opt for maintenance despite moderate toxicity. Subsequent questions included cost and toxicity considerations and required pts to identify minimum acceptable duration of OS benefit to estimate more precisely a meaningful clinical benefit. If treatment was free, had no toxicity, and the OS benefit was 1 yr or less, 49% would choose maintenance (see Figure). In the same scenario, if toxicities were mild, the proportion of pts who choose maintenance was similar (46%). If pts experienced moderate toxicity, 42% choose maintenance. With rising financial burden (out-of-pocket) and toxicity, the proportion of pts who choose maintenance declined (see Table). For example, if the cost was $25/mo, mild toxicity experienced, and the OS benefit was one year or less, 46% would choose maintenance, while 39% of pts would choose maintenance if it cost $250/month and there was moderate toxicity. If maintenance cost $10,000/mo and was associated with mild or moderate toxicity, 18% and 17% of pts would choose treatment, respectively. Conclusions: For the first time, we have described the broad range of patient perspectives regarding trade-offs in the treatment of MM with maintenance therapy. We found that willingness to be treated with maintenance declined when actual benefits were provided in concrete numeric terms compared with a general statement of PFS benefit. The discrepancy between the 92% of pts choosing to undergo maintenance if free and mild toxicity when there is a PFS benefit but no OS benefit, compared to 49% of pts choosing maintenance if free, mild toxicity, and associated with an OS benefit of 1 yror less; suggests pts have difficulty understanding the concept of PFS. We also found that the magnitude of benefit required to consider maintenance was affected by cost and toxicity. In our experience, pts typically incur a cost of approximately $25/mo and experience mild toxicity. In this study, nearly half (46%) of such pts would opt for maintenance if the OS benefit was 1 year or less while only 33% of pts would opt for maintenance if the OS benefit was 6 months or less. Our data implies that good care in MM requires detailed conversations about each and every patient's priorities and expectations prior to making recommendations for or against such treatments. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 1861 Idiopathic Bence Jones Proteinuria (Smoldering Monoclonal Light-Chain Proteinuria), first reported in 1982, is an asymptomatic plasma cell proliferative disorder associated with an elevated risk of progression to symptomatic MM or amyloidosis (AL). We defined it as the presence of a monoclonal light chain in the urine ≥200 mg/24h, absence of an intact immunoglobulin M protein (IGH expression) in the serum and no evidence of MM, AL or other related plasma cell proliferative disorders. Following approval by our Institutional Review Board, we searched a computerized database and reviewed the records of all patients seen at Mayo Clinic within 30 days of the recognition of a monoclonal light chain (Bence Jones protein) in the urine from January 1, 1960 through June 30, 2004. Patients with end-organ damage at diagnosis resulting from the plasma cell proliferative disorder (including MM or AL), or who had received chemotherapy or had a nephrotic syndrome were excluded. Follow-up included review of each patient's medical record at Mayo Clinic, as well as review of death certificates for patients who died. Patients were sent letters of inquiry if they had not visited Mayo Clinic in the preceding year. The risks of progression to MM and AL were compared to those expected on the basis of Surveillance, Epidemiology and End Results (SEER) rates for MM in Iowa and the incidence of AL in Olmsted County, Minnesota. One-hundred and one patients fulfilled the criteria for diagnosis during the 44-year period (1960–2004). The median age at diagnosis was 67 years (range 18–90 years), and only 2% were < 40 years old. Seventy-three percent were male. The urine M protein ranged from 200 mg/24h to 4.7 g/24h (median value, 500 mg/24h); 29% had > 1 g/24h. Kappa light chain accounted for 50% while the remaining 50% were lambda. Fifty-seven (56%) had a monoclonal light chain in the serum on immunofixation. Concentrations of uninvolved (normal, polyclonal or background) immunoglobulins were reduced in 62%. Eighty-eight percent of patients died during follow-up. During 900 person years of follow-up, 29 patients developed symptomatic MM (relative risk, 140.3; 95% CI, 93.9–201.5) and an additional 9 patients developed AL (relative risk, 104.4; 95% CI, 47.8–198.4). Four patients had both multiple myeloma and AL amyloidosis. The cumulative probability of progression to active MM or AL was 19% at 5 years, 31% at 10 years and 42% at 15 years. The factors associated with progression to MM or AL included size of urine M protein, percentage of bone marrow plasma cells, serum free light chain ratio < 1/100 or > 100, serum creatinine and reduction of all 3 uninvolved immunoglobulins. We conclude that patients with Idiopathic Bence Jones Proteinuria (Smoldering Monoclonal Light-Chain Proteinuria) are at risk for the development of MM or AL and must be followed indefinitely. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 1802 Poster Board I-828 Background Heterogeneity in multiple myeloma (MM) leads to disparate outcomes with a wide variation in overall survival (OS). Based upon the evidence predominantly gathered from newly diagnosed patients treated with standard chemotherapy and/or transplantation, the current Mayo (mSMART) prognostic model uses a combination of metaphase cytogenetics, fluorescence in-situ hybridization (FISH) and plasma cell labeling index (PCLI) for risk-stratification at diagnosis of MM. The objective of our study was to evaluate the significance of this stratification model in the era of novel therapies, and to assess the independent prognostic value of each of the components in the model. Methods Data were abstracted from a cohort of 1556 consecutive patients with MM who presented to our institution between January 1999 and March 2009 within ninety days of diagnosis of MM A total of three hundred and eighty six patients had been evaluated with conventional cytogenetics near diagnosis in addition to interphase FISH. Out of this cohort, three hundred and sixty six patients had availability of all the three tests, including the slide-based PCLI. High-risk MM was defined as presence of any one or more of the following: cytogenetics: hypodiploidy, monosomy of chromosome 13 or deletion 13q ; FISH: deletion of p53 (locus 17p13) or immunoglobulin heavy chain (IgH) translocations, t(4;14) (p16.3;q32) or t(14;16)(q32;q23); PCLI ≥3%. Survival estimates were created using the Kaplan-Meier method and compared by log-rank tests. The impact of each of the three tests was assessed by a multivariate (MV) analysis using Cox proportional hazards model. Results The median OS of the cohort of 366 patients was 65 months from presentation. One hundred and twelve (31%) patients were deemed high risk by any one or more of the three tests: Metaphase cytogenetics, FISH or PCLI (current mSMART definition of high-risk MM). The median OS of high risk patients was 52 months versus 71 months for standard-risk (P=0.007). We then studied the prognostic value of the three tests separately. Patients classified as high risk by FISH had a median OS of 35 months versus 65 months for the standard risk, HR= 2.3, P<0.001. Similarly, cytogenetics alone was also able to classify patients into high and standard risk with a comparable HR of 2.1 (P=0.008, median survival 37 vs. 64 months). In contrast, PCLI did not have a significant prognostic value (HR =1.41, P=0.32). This was confirmed on multivariate analysis in a model that included all 3 tests. FISH (HR=2.36, P=0.001) and cytogenetics (HR=1.99; P=0.017) emerged as independent determinants of prognosis in the multivariable analysis, while PCLI (HR=1.03, P=0.93) did not provide additional prognostic value. We then examined whether the prognostic value of FISH contributed additionally in patients classified into high and standard risk by conventional cytogenetics, and vice versa. Those classified as high risk by cytogenetics (n=44, 11 %), were further categorized into 2 groups by additional prognostic information obtained by FISH (median survival 18 vs. 52 months; P=0.005). Similarly, those classified as standard risk by cytogenetics (n=342, 89 %), were further categorized into 2 groups (median survival 52 vs. 71 months; P=0.017) by additional FISH-based stratification. Similarly, high-risk patients defined by FISH (n=65, 17 %) were further classified into 2 groups with significant difference in median OS (18 vs. 52 months, P=0.004), based on the presence or absence of high-risk features on cytogenetics. In contrast, no additional prognostic information was gained by cytogenetics in patients who were stratified as standard risk by FISH alone (n=321, 83%). Conclusion Our study validates high risk features defined by FISH and conventional cytogenetics in the mSMART risk stratification model among patients treated after the introduction of novel therapies. Either test identifies a high risk cohort with a hazard ratio of approximately 2 (median survival ∼37 versus ∼65 months). In patients known to have high risk disease by one of the two tests, knowledge of the other appears to add additional prognostic value. Disclosures Fonseca: Amgen, BMS, Celgene, Otsuka, Genzyme and Medtronic: Consultancy. Gertz:celgene, millennium: Honoraria. Dispenzieri:celgene: Research Funding. Kumar:celgene, genzyme, millennium, novartis, bayer: Research Funding; genzyme: Membership on an entity's Board of Directors or advisory committees.

Abstract Abstract 946 Background: The emerging therapies directed at the plasma cell clone have dramatically increased overall survival (OS) for both myeloma and amyloidosis patient populations. As more treatment trials are done in patients (pts) with AL, benchmarks for outcomes among previously treated AL pts are required, especially for those pts who are not candidates for high-dose chemotherapy with peripheral blood stem cell transplantation (ASCT). Inadequate information is available about the number of non-transplant pts who go on to receive second line treatment for AL amyloidosis. Methods: To ascertain the outcomes of pts who did not receive ASCT as primary therapy but who required a second line of therapy, we reviewed the experience of pts seen at Mayo Rochester between 1990 and 2010 according to an IRB approved retrospective review protocol. 1828 pts had their first Mayo visit for AL during this time period. Pts were excluded from this study for the following reasons: 571 had upfront transplant; 907 pts had received only one line of treatment for their amyloid; 91 had longstanding other associated malignancy [Waldenstrom's macroglobulinemia (8), lymphoma (15), CLL (6), multiple myeloma (62)]; and 93 had inadequate follow-up information. One-hundred and sixty-six pts received 2 or more lines of therapy for their AL amyloid and are the subject of these analyses. Statistical analyses were done using JMP statistical software (SAS, Carey, NC). Results: Of the 166 pts, the median age was 64 years (range 34, 84). 49% were male. Baseline organ involvement was as follows: cardiac 84/166 (50%); renal 118/166 (71); liver 23/166 (13.8%); peripheral nerves 19/166 (11.4%); and gastrointestinal 14/166(8.4%). Thirty-one percent (52/16) had both cardiac and renal involvement. Only 73 pts had cardiac biomarkers (NT pro BNP and Troponin T) done at baseline. Of these pts, 26% were stage 1, 49.3% were stage 2, and 24.6% were stage 3 according to original Mayo cardiac biomarker staging system. By inclusion criteria definition, all 166 pts received 1st and 2nd line therapies; 53 (32%) pts received 3rd line of treatment; 20 (12%) received 4th line of treatment; and 10 (6%) received 5th line of treatment. For first line therapy, the most common drugs given either singly or in combination were corticosteroid (147/166; 88.5 %), alkylator (99/166; 59.6%), IMID (34/166; 20.4 %), and bortezomib (19/166; 11.4%). The median time from diagnosis to 2nd line therapy was 10.3 months. Second line regimens received included: corticosteroid, 108/166 (65.1%); alkylator, 76/166 (45.8 %); IMID, 46/166 (27.7%); and bortezomib, 46/166 (27.8%). The median time from diagnosis to 3rd line therapy was 19.8 months. For the 53 pts who received 3rd line treatment, regimens included: corticosteroid, 41/53 (77.3%); IMIDs, 17/53 (32.1%); alkylator, 17/53 (32.1%); bortezomib, 12/53 (22.6%). The median time from diagnosis to 4th line therapy was 31.8 months. For the 20 pts receiving 4th line treatment, regimens included: corticosteroids, 15/20(75%); alkylator, 12/20 (60%), bortezomib, 7/20 (35%); and IMIDs, 4/20(20%). Eighty-three pts have died. The 1 year mortality of our study population was only 8%. The median follow-up of surviving pts was 47.6 months. Figure 1 demonstrates Kaplan-Meier estimates of overall survival (OS) from initiation of each successive therapy. The median OS from initiation of 1st, 2nd, and 3rd lines of treatment were 65, 49.5 and 36.7 months respectively. The median OS after the 4th line of treatment was not reached. The 4 year OS rates from initiation of 1st, 2nd, 3rd and 4th lines of therapy were 58%, 50.8 %, 50 % and 53.4% respectively. Conclusion: Outcomes among relapsed or refractory AL pts are better than what one might expect. Multiple publications have demonstrated that the 1 year mortality of newly diagnosed AL is in the vicinity of 40%. Thereafter, the rate at which pts die dramatically decreases. Our study provides explicit data characterizing the fate of pts unfortunate enough to require additional therapy but fortunate enough to survive past the exceedingly high risk period of death that occurs within 6–12 months of diagnosis. These data provide useful information for benchmarking future trials for treatments of AL amyloidosis. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 1988 Background With the utilization of novel agent-based combination therapies and autologous stem-cell transplantation (ASCT) in multiple myeloma (MM), the rigorous response category of stringent complete remission (sCR) in the international uniform response criteria is increasingly becoming attainable. In addition to the standard criteria for complete remission (CR), sCR requires normalization of the free light chain ratio and disappearance of clonal cells as determined by the marrow immunofluorescence or immunohistochemistry. We have previously validated the new response category of sCR created in by the International Myeloma Working Group and demonstrated that sCR represents a deeper level of response, translating into a superior OS. Herein we report the survival outcomes of patients attaining sCR or standard CR, from a 2-year landmark after ASCT in a cohort of patients with extended follow-up. Additionally, we report the outcome of patients who remained in sCR for at least 6 months (sustained-sCR) after ASCT. Patients and Methods Maximal response rates of four hundred and forty-five consecutive patients who underwent ASCT within 12 months of diagnosis of MM were determined. The population achieving varying degrees of complete remission (n=237) is the focus of this study. We performed a landmark analysis 2 years after ASCT to ensure that all the patients attaining at least CR had sufficient time to reach the response levels being studied. Patients were categorized as having sustained sCR (sus-sCR) if the duration of sCR was at least 6 months. Overall survival (OS) was estimated by the Kaplan Meier method and the survival curves were compared by log-rank test. Results The median follow-up of the entire cohort was seventy-seven months (95% CI: 73–82 months). The sCR rate after ASCT was 24% (n=109). Median time to progression (TTP) of patients attaining sCR was 50 months from ASCT, and median overall survival (OS) is not reached, in contrast to those attaining standard CR (n=37, TTP=20 months, OS=81 months) or near CR/nCR (n=91; TTP= 19 months, OS=60 months, p<0.0001 for both TTP and OS). OS of patients surviving at least 2 years from ASCT (Figure 1a) continued to remain superior for those attaining sCR (n=105, median: not reached) versus 70 months for the CR group (n=32; p=0.004). Among patients achieving sCR (n=109), OS of patients with sus-sCR (n= 75) at 6 months from ASCT is not reached (5-year OS=91%, 7-year OS=86%) versus median OS of 66 months (5-year OS=49%, 7-year OS=37%; p<0.0001) for those who had non-sustained-sCR (n=34) after ASCT (Figure 1b). Conclusion In our landmark analysis of patients with MM who survived at least 2 years from ASCT, those attaining sCR have a markedly superior outcome compared to those attaining standard CR. However, among patients attaining sCR, those with sustained sCR of 6 months or greater had the best outcome. Myeloma trials reporting response rates should identify patients achieving sCR and CR separately owing to markedly disparate outcomes of the two categories. Disclosures: No relevant conflicts of interest to declare.

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 Abstract 1803 Poster Board I-829 Background Plasma cell proliferative disorders are monitored by a variety of methods. Serum protein electrophoresis (SPEP) and/or urine PEP M-spike quantitation are commonly assessed in patients with monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and multiple myeloma (MM) to determine disease progression, response, or relapse. Serum immunoglobin (Ig) concentrations can be quantitated when the M-spike is large or if the migration is obscured within the SPEP beta fraction. Serum FLC quantitation provides a rapid indicator of response, will detect the rare occurrence of FLC escape, and will allow disease monitoring in the absence of a measurable serum or urine M-spike. The International Myeloma Working Group (IMWG) has recommended that the serum and urine M-spike should be used to monitor disease, and that FLC quantitation should be used only if there is no measurable disease by electrophoresis and if the monoclonal FLC concentration is greater than 10 mg/dL in the context of an abnormal FLC K/L ratio. We have studied serial samples in clinically stable patients in order to assess the total variability (analytic and biologic) of these assays and to confirm the IMWG recent recommendations. Methods Serial data from stable MGUS patients (n=35) were identified by the availability of all 3 serum test results (M-spike, Ig, FLC) in at least 4 serial samples that were obtained 9 months to 5 years apart and whose serum M-spikes varied by less than 25%. For MM (n=60) and SMM (n=48) the samples were within 9-15 months and serum M-spikes varied by less than 0.5 g/dL. Among the 60 MM, 48 SMM, and 35 MGUS patients, there were 23, 41, and 18 patients with measurable disease by serum M-spike (i.e. M-spike >1 g/dL); 19, 10, and 10 patients with an evaluable FLC (i.e. monoclonal FLC > 10 mg/dL and an abnormal FLC ratio); and 5, 5, and 1 patient with an evaluable urine (i.e. M-spike > 200mg/24 hr). The FLC data was analyzed as the involved FLC concentration (iFLC), the difference between the involved and uninvolved FLC concentration (dFLC), and the FLC K/L ratio (rFLC). The coefficients of variability (CV) were determined for each methodology in each patient sample set, and the average CVs were determined. Igs were quantitated by immunonephelometry using a Siemens BNII and Siemens reagent sets; kappa and lambda FLC were quantitated using a Siemens BNII and Freelite reagent sets from The Binding Site; M-spikes were quantitated using Helena SPIFE SPE and reagent sets. Results The CVs for the Ig quantitation, SPEP M-spike, FLC quantitation, and urine M-spike in each of the patient groups are listed in the table: Our laboratory's interassay analytic CV for replicate samples are 4-5% for Ig quantitation, 6-8% for SPEP M-spikes, 6-7% for FLC quantitation, and 5-7% for urine M-spikes. The analytic CVs of the methods are similar, but the total (analytic + biologic) CVs are very different. The samples have been selected by restricting the variability of serum M-spike values; when we apply the same criteria to the IgG quantitation, the IgG total CV comes closer to the serum M-spike CVs. The remaining differences, however, may be due to biologic variability contributed by polyclonal Ig. The total CV for iFLC is similar to the urine M-spike CV and suggests a previously unrecognized large biologic CV for serum FLC. The iFLC and dFLC CVs were comparable but were smaller than the rFLC CV. Conclusion The variability of the serum and urine M-spike, Ig, and FLC measurements confirm the IMWG recommendations for patient monitoring. If a patient has a measurable M-spike >1 g/dL, then the serum M-spike should be followed. If there is no measurable disease, then the iFLC can be monitored, provided that the rFLC is abnormal and the iFLC concentration is >10 mg/dL. Although the number of patients with evaluable urine M-spikes in this study is small, larger studies may confirm the utility of serum FLC compared to urine M-spike for monitoring patients with monoclonal gammopathies. Disclosures No relevant conflicts of interest to declare.