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Abstract Abstract 596 Background Large population-based studies have demonstrated a significant improvement in survival (OS) for patients (pts) with multiple myeloma (MM) over time since the mid-1990s. The improvement has mostly affected younger patients suggesting a beneficial impact of AHCT. The availability of novel drugs within the last decade and their impact on the utilization and outcomes of AHCT recipients is unknown. Methods We retrospectively reviewed the characteristics and outcomes of 20,278 patients undergoing AHCT within 12 months of diagnosis in USA and Canada and reported to CIBMTR in the periods of 1995–1999 (n=2226), 2000–2004 (n=6408) and 2005–2010 (n=11644) including a subgroup of 4373 individuals with detailed patient, disease and treatment information. We subsequently compared survival and analyzed patient, disease and treatment characteristics across the three periods with the time period serving as a surrogate for pre- and post-transplant exposure to novel agents. Results Across the 3 time periods, there was a marked increase in the number of upfront transplants across all age groups (Figure 1a). Patients receiving upfront HSCT in the more recent period were older, less likely to have stage 3 MM at diagnosis and more likely to have received thalidomide (<1 % vs. 22% vs. 52%), lenalidomide (0% vs. <1% vs. 21%) or bortezomib (0% vs. 2% vs. 35%) and have chemosensitive disease at the time of AHCT. The proportion of African-American patients remained low and stable across the three periods (14 vs. 13 vs. 15%). Over the 3 periods, there was a decrease in chemotherapy based stem cell mobilization and increase of single agent G-CSF based mobilization (24% vs. 24% vs. 41%). The use of single agent Melphalan conditioning increased from 54% in 1995–1999 to nearly 100% in the latest period concomitant with near disappearance of total body irradiation-based and multi-drug conditioning regimens. Compared with 1995–99 cohort, survival was superior in the 2000–04 and 2005–09 cohorts at 24 (72% vs. 79% vs. 84%, P<0.001), 48 (54% vs. 60% vs. 64%, P<0.001) and 60 months (47% vs. 52% vs. 55%, P<0.001) (Figure 1b). In multivariate analysis, we found that transplant in the 2000–04 period (HR=0.77, 95% C.I. 0.67–0.89) or in the 2005–10 period (HR=0.68, 95% C.I. 0.59–0.79) along with Karnofsky performance score of 80–100 (HR=0.59, 95% CI 0.51–0.70) and chemosensitivity (HR= 0.76, 95% C.I. 0.66–0.87) were associated with lower risk of death. Factors associated with higher risk of death were age 50–65 (HR=1.29 95% 1.13–1.47), age 65–80 (HR=1.45, 1.23–1.72), Durie-Salmon or ISS stage III at diagnosis (HR 1.56, 95% C.I. 1.39–1.76) and more than one prior line of therapy (HR=1.15, 95% C.I. 1.03–1.28). In comparison to patients transplanted in 1995–99, post relapse survival was superior for patients transplanted in 2000–04 and 2005–10 at 24 months (58% vs. 65% vs. 72%, P=0.005 and <0.001 respectively) and 48 months (33% vs. 39% vs. 40%, P=0.023 and 0.033 respectively). The use of maintenance therapy has changed with 27% in 1995–99 receiving planned interferon vs. 23% in 2005–09 receiving planned thalidomide, lenalidomide or bortezomib maintenance. Conclusions Utilization of upfront AHCT is increasing in the USA, particularly in older patients. Improvement in survival for MM patients seen in population studies results not only from greater utilization of AHCT but also from the improvement in outcomes after AHCT and a significant recent improvement in post-relapse survival. Pre- and post-transplant exposure to novel agents likely contributes to survival. AHCT and novel agents are complementary and should be combined for the optimal management of newly diagnosed MM. 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.

Abstract Abstract 1364 In light chain (AL) amyloidosis, as well as in multiple myeloma, response to treatment is increasingly being used as a surrogate endpoint in clinical trials. In 2005 a consensus statement of the International Society of Amyloidosis (ISA) established the criteria for hematologic and organ response. Since then, several studies emphasized the prognostic relevance of the measurement of the amyloidogenic precursor, the circulating free light chain (FLC). Moreover, it was reported that patients who with treatment achieved decreases in the cardiac biomarker N terminal natriuretic peptide type B (NT-proBNP) had longer survival, although echocardiographic criteria of response were not attained. The ISA Consensus Panel reconvened in 2010 to update hematologic and organ response criteria. The panel felt that any new criteria should be validated in a large patient population. Thus, we systematically gathered from 7 referral centers in Europe and in the United States a cohort of 649 patients with systemic AL amyloidosis who had been evaluated for hematologic and organ responses at diagnosis and 6 months after treatment initiation, excluding patients who died earlier. At diagnosis, 430 patients (66%) had heart involvement, 377 (58%) had NT-proBNP ≥650 ng/L, 455 (70%) had renal involvement (95, 15%, with glomerular filtration rate <30 mL/min) and 100 (15%) had liver involvement. Two-hundred eighty-nine patients (44%) were treated with melphalan and dexamethasone, 118 (18%) received thalidomide based therapy, 73 (11%) underwent autologous stem cell transplant, 35 (5%) were treated with regimens including lenalidomide, 20 (3%) received bortezomib-based therapy, and the rest received other alkylating agents, nucleoside analogues or dexamethasone. The median follow-up of living patients was 24 months, and 233 patients (34%) died. The ability of response criteria to identify patients who died was compared by evaluating the areas under Receiver Operator Characteristic curves based on death at 1 year, and by calculating the Harrell C statistic and the Royston explained variation. Survival was calculated from the time of evaluation of response. We maintained the category of complete response (CR: negative serum and urine immunofixation, normal FLC kappa/lambda ratio and normal marrow studies) and examined candidate criteria for partial (PR) and very good partial responses (VGPR), based on percentage changes or absolute values achieved after treatment of involved (amyloidogenic) FLC (iFLC), and alternatively on the difference between iFLC and uninvolved FLC (dFLC). With respect to cardiac response and progression, NT-proBNP-based criteria were defined as a decrease or an increase of both >30% and >300 ng/L, and a threshold of evaluability based on NT-proBNP baseline level >650 ng/L was chosen. The most powerful criteria for PR were those based on dFLC percent decrease, and a 50% cutoff was preferred because of easier clinical use. Among candidate criteria for VGPR, the best were based on iFLC absolute value achieved after therapy, but the performance of those based on dFLC absolute value was only slightly lower. Therefore, a definition of VGPR based on dFLC (<40 mg/L) was adopted for the sake of harmonization with the dFLC-based definition of PR. The adopted hematologic response criteria and their prognostic significance are reported in Table 1. These criteria identified 4 groups with significantly different survivals (Figure 1). Also the proposed criteria of NT-proBNP response and progression were significantly associated with survival (Figure 2). Our 2010 revised consensus criteria for hematologic response include maintenance of the definition of CR, and with use of dFLC re-casting the definition of PR and introducing a VGPR category, and for cardiac response and progression introducing the use of changes in NT-proBNP levels. In a further analysis we will address the definition of measurable dFLC at baseline and evaluate the applicability of the response criteria to earlier evaluation of response. The revised criteria improve the framework for clinical research in AL. Disclosures: Off Label Use: Thalidomide, lenalidomide, bortezomib for systemic AL amyloidosis. Dispenzieri:The Binding Site: Honoraria. Gertz:Celgene: Honoraria; Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees. Dimopoulos:Ortho-Biotech: Honoraria; Celgene: Honoraria; Millennium: Honoraria. Merlini:Millennium: Honoraria; Ortho-Biotech: Honoraria.

SummaryIbrutinib‐related data in Waldenström macroglobulinaemia (WM) remain sparse, particularly outside of trials. We report on 80 patients [previously treated, n = 67 (84%), treatment‐naïve, n = 13 (16%)] with WM, evaluated consecutively at Mayo Clinic, who received ibrutinib off‐study after its approval in 2015 for WM. Overall response rate (ORR) was 91%; major‐response rate (MRR) was 78%. The median time to first response and best response was 2·9 [95% confidence interval (CI): 2–4] and 5·7 (95% CI: 4–12) months, respectively. The median follow‐up was 19 (95% CI: 14–21) months; 18‐month progression‐free survival (PFS) was 82%. The median time on therapy was 12·5 (95% CI: 9·3–16·7) months, and the median duration‐of‐response was 32 (range: 23–32) months. Twenty‐five patients (31%) had discontinued therapy at last follow‐up (68% due to treatment‐related toxicities) and 18% of patients required dose reduction. Fatigue (12%) and atrial‐fibrillation (11%) were common non‐haematological toxicities. IgM rebound occurred in 36% of patients who abruptly discontinued ibrutinib. Following ibrutinib discontinuation, 84% of patients received subsequent treatment, achieving an ORR of 57% and MRR of 50%. The median PFS from commencement of subsequent salvage therapy was 18 months. Ibrutinib therapy, outside of clinical trials, is effective in WM, but is associated with toxicities and challenges, including IgM rebound and a high drug discontinuation rate for reasons other than disease progression.