Go, Ronald S.

Abstract Erdheim-Chester disease (ECD) is a rare histiocytosis that was recently recognized as a neoplastic disorder owing to the discovery of recurrent activating MAPK (RAS-RAF-MEK-ERK) pathway mutations. Typical findings of ECD include central diabetes insipidus, restrictive pericarditis, perinephric fibrosis, and sclerotic bone lesions. The histopathologic diagnosis of ECD is often challenging due to nonspecific inflammatory and fibrotic findings on histopathologic review of tissue specimens. Additionally, the association of ECD with unusual tissue tropism and an insidious onset often results in diagnostic errors and delays. Most patients with ECD require treatment, except for a minority of patients with minimally symptomatic single-organ disease. The first ECD consensus guidelines were published in 2014 on behalf of the physicians and researchers within the Erdheim-Chester Disease Global Alliance. With the recent molecular discoveries and the approval of the first targeted therapy (vemurafenib) for BRAF-V600–mutant ECD, there is a need for updated clinical practice guidelines to optimize the diagnosis and treatment of this disease. This document presents consensus recommendations that resulted from the International Medical Symposia on ECD in 2017 and 2019. Herein, we include the guidelines for the clinical, laboratory, histologic, and radiographic evaluation of ECD patients along with treatment recommendations based on our clinical experience and review of literature in the molecular era.

e19523 Background: Previous studies have shown a disparity in outcomes of MM between clinical trials and real-world practice. This could be partly due to clinical trial exclusion of patients who need urgent treatment due to high burden of disease or significant illness. In this study, we aim to analyze the impact of time to initiation of systemic therapy for MM on overall survival (OS). Methods: We included MM patients reported to National Cancer Data Base (2004-2014). We excluded 2,860 patients with suspected smoldering MM due to initial treatment beyond 120 days. Relative risk of delayed time to systemic therapy was assessed by logistic regression model. Kaplan-Meier method and Cox multivariate analysis were used to evaluate the association between time to therapy and OS. Results: A total of 53, 519 MM patients were included. Median time to systemic therapy in our cohort was 18 days (range 0-120). Of the entire cohort, 24% patients received systemic therapy for MM < 7 days from diagnosis, and 32% received it after 30 days. Factors associated with time to systemic therapy > 30 days were Black race (OR 1.12, CI 1.07-1.16), female sex (OR 1.10, CI 1.06-1.14), lower Charlson comorbidity score (OR 1.36, CI 1.28-1.45), and academic facility (OR 1.18, CI 1.13-1.24). The median OS for patients who initiated therapy > 30 days after diagnosis was longer than those who received it within 7 days (37 vs. 29 month, p < 0.001). Similarly, on multivariate analysis, patients who received treatment > 30 days after diagnosis were found to have a lower mortality as compared to those who initiated treatment < 7 days (HR 0.81, CI 0.79-0.83; Table). Conclusions: In our study, time to initiation of systemic therapy was an independent prognostic factor in MM. This could be related to the high-risk nature of disease of patients treated within a short duration of diagnosis. These findings have implications for future clinical trial design, which should allow for a pragmatic approach toward enrollment of these high-risk patients to improve external validity. [Table: see text]

e19519 Background: NSMM is a rare subtype of myeloma that has not been well characterized in the era of novel agent induction therapy. Thus, we evaluated the clinical and cytogenetic features of patients with newly diagnosed NSMM evaluated at our institution. Methods: We evaluated all NSMM patients seen at the Mayo Clinic, Rochester from 2008-2017 based on the absence of a detectable monoclonal protein in their serum and urine electrophoresis and having a concurrent involved serum immunoglobulin light chain of less than 5 mg/dL. Survival analysis was performed by the Kaplan-Meier method and clinical and cytogenetic features were reported descriptively. Results: This cohort consisted of 30 consecutive patients with NSMM with a median age of 62 years (40-79) of which 16 (53%) were male. The median bone marrow plasma cell involvement was 70% (Range: 0 – 100). There were 3/25 (12%) patients who presented with a creatinine of 2 mg/dL or greater and 6/23 (26%) patients who presented with hypercalcemia (11 mg/dL or greater). The ISS classification of this cohort is as follows: Stage 1- 8 (36%) patients, Stage 2- 3 (14%) patients and Stage 3- 11 (50%) patients. There were 6 (21%) out of 28 patients with high risk cytogenetics (either del 17p, t(4;14), t(14;16) or t(14;20). The distribution of primary cytogenetic abnormalities among this cohort was as follows: t(11;14) – 16 (57%), t(4;14) – 1 (4%), trisomies – 6 (21%) and other - 5 (13%). The median overall survival (OS) for patients in this cohort was 59 months (95% CI: 34 – 64). In comparison to a control cohort of newly diagnosed secretory myeloma patients matched for age, gender and year of diagnosis in a 1:2 ratio, the median OS was worse for the NSMM cohort but this was not statistically significant (59 vs. 92 months, p = 0.257). Conclusions: Patients diagnosed with NSMM had a predisposition towards having a t(11;14) primary cytogenetic abnormality. In the era of novel agent induction therapy, they may have a survival outcome that may be worse than newly diagnosed secretory myeloma patients.

8039 Background: Treatment of MM has evolved significantly over the past decade, with increasing use of multi-drug combinations for initial therapy. In addition, supportive care approaches have also improved. We examined how these improvements have translated to survival outcomes in patients with newly diagnosed MM. Methods: Patients (n=3449) with a diagnosis of MM made between 2004 and 2017 and seen at Mayo Clinic within six months of the diagnosis, were included in this analysis. Patients were divided into three groups based on the year of diagnosis; group 1- 2004-07 (n=831), group 2-2008-12 (n=1161), and group 3-2013-17 (n=1457). Survival of the groups were estimated using Kaplan-Meier method, and compared using log rank test. Results: The median age was 64 years (22 to 96); 60% were male and 40% were female. 14% were >75 years, 33% were aged 65-75 and 53% were <65 years. The median overall survival for the whole cohort was 5.7 years (95%CI; 5.4, 6.3). The median OS for the groups 1, 2 and 3 were 3.9, 6.3 and NR, respectively; p<0.001. The 4-year survival estimates were 50%, 62%, and 75%, respectively. We then explored the improvements in patient subgroups. While all patients experienced improvements in OS over time, improvement in group 3 was most prominent for those >75 years. In patients <65 years, the 4-yr OS for groups 1, 2 and 3 were 57, 71, and 79% respectively. In patients 65-75 years of age, the 4-yr OS for groups 1, 2 and 3 were 48, 60, and 75% respectively. In patients >75 years, the 4-yr OS for groups 1, 2 and 3 were 24, 35, and 56% respectively. While patients with high-risk disease did not see as much benefit in the earlier period, substantial progress was seen in the last group. The 3-yr OS for patients with high-risk cytogenetics were 52, 55, and 73% for groups 1, 2 and 3 compared to 67, 75, and 85% for standard-risk cytogenetics respectively. 2067 patients were staged according to the International Staging System and the median OS for stages 1, 2 and 3 were 6.5, 4.6 and 2.4 in group 1; 9.2, 6.6 and 3.5 in group 2 and NR for any of the stages in group 3. Conclusions: The results confirm continued improvement in survival of newly diagnosed multiple myeloma patients, including elderly and high-risk MM.

8034 Background: Minimal residual disease (MRD) assessment in multiple myeloma (MM) has improved our ability to assess disease activity, resulting in more advanced prognostication. While MRD assessment remains confined to the bone marrow (BM) plasma cell population, serum studies including immunofixation (IFE) are required to complete response evaluation. The significance of those who are MRDneg yet have detectable monoclonal protein through IFE remains unclear. Methods: We retrospectively studied 256 MM patients who had MRD assessment via the Euroflow multiparametric flow cytometry on the BM with concomitant serum IFE testing. Patients who were MRDneg were included in the study. Outcomes included probability of disease progression (PD) at 1 year. The Cox-proportional hazards model was used to compare probability of PD among different groups. Time to progression (TTP) was calculated as the difference from date of MFC analysis to PD in months. Results: Among the entire cohort, 178 (70%) patients were MRDneg and median follow-up from MRD assessment was 6.3 months. Among these patients, 74 (42%) had a positive IFE at the time of MRD analysis. Within the MRDneg/IFEpos group, 31 (42%) patients remained IFEpos after a median follow up of 5.5 mo from initial MRD/IFE testing while 34 patients eventually became IFEneg after a median of 2.8 mo with no subsequent IFE available in 9 patients. The 1 year probability of PD in the MRDneg/IFEneg group was 20% compared to 41% in the MRDneg/IFEpos group (P < 0.01, Wilcoxon test). When comparing subsequent IFE status in those who were MRDneg/IFEpos, those who remained IFEpos had a trend towards shorter TTP compared to patients who later became IFEneg. Conclusions: Persistent monoclonal protein in the face of MRD negativity predicts for a shorter TTP. This likely reflects persistent disease that was not sampled on the BM aspirate in many of these patients compared to those who eventually become IFEneg with a trend towards longer TTP owing to the prolonged half-life and therefore clearance of M protein. This supports the current strategy of assessing for MRD at the time of suspected complete response to reduce the chance of positive MRD tests and thus avoidance of multiple BM exams.

8031 Background: Our prior studies identified the prognostic significance of ≥400 cPCs/150,000 analyzed events quantified by MFC in NDMM. We evaluated if a similar quantification of cPCs using MFC can add prognostic value to the current R-ISS classification of NDMM pts. Methods: We evaluated all NDMM pts seen at the Mayo Clinic, Rochester from 2009-2017 who had their peripheral blood samples evaluated by 6-color MFC prior to therapy. The cPCs detected were reported as the number of clonal events/150,000 collected total events. Survival analysis was performed by the Kaplan-Meier method and differences assessed using the log rank test. Results: This cohort consisted of 566 consecutive pts with NDMM with a median age of 66 years (27-95). The distribution of the R-ISS classification of this cohort is as follows: Stage 1- 128 (23%) pts, Stage 2- 369 (65%) pts and Stage 3- 69 (12%) pts. The median number of cPCs was 59 (0-46,412) / 150,000 events. The median time-to-next-treatment (TTNT) and overall survival (OS) for pts with ≥400 cPCs (n = 140, 25%) was 19 months and 46 months compared with 34 months and 77 months for those with < 400 cPCs respectively (n = 426, 75%) (p < 0.001 for both). The median TTNT and OS for pts based on their R-ISS classification as well as with and without the presence of ≥400 cPCs by MFC was as follows in the following Table. Conclusions: Quantifying ≥400 cPCs/150,000 analyzed events by MFC can potentially upstage the R-ISS classification of a subset of NDMM pts with stage I and II disease and identify those pts with a worse than expected survival outcome.[Table: see text]

8019 Background: POEMS syndrome is a rare paraneoplastic syndrome caused by an underlying plasma cell disorder. Most of the information regarding treatment has been gleaned from retrospective data. The combination of a proteasome inhibitor, an IMiD and corticosteroid is known to be highly effective among patients with myeloma. Methods: We designed a pilot using a 28-day oral regimen of ixazomib (4 mg days 1, 8, 15), lenalidomide (25 mg days 1-21), and dexamethasone (20 mg days 1, 8, 15, 22). Aspirin and acyclovir were used for prophylaxis. Eligibility included a diagnosis of POEMS syndrome, a plasma VEGF > 200 pg/ml, a PS < 3. There were two groups [gp] (intended enrollment 15 per gp): Gp A, 13 cycles for patients (pts) who had relapsed or refractory disease; Gp B, 3 cycles for pts destined for high-dose chemotherapy with stem cell transplant. Primary endpoint was VEGF complete response (CR = normalization) after 3 cycles. Secondary endpoints included safety, hematologic response, and overall survival at 3 and 12 months. Other domains including PET response, clinical responses including neurologic response were also studied. To date, 13 pts enrolled since 10/31/2016—4 to Gp A and 9 to Gp B. 11 pts were analyzed (2 dropped out before receiving any therapy). Data were frozen as of 1/21/2019. Results: Median age was 55; 73% were male. So far, overall 64% met primary endpoint of VEGF CR (Table). The median follow-up of survivors is 12.4 mo (6, 24). 1 pt came off study for non-responsive disease and died thereafter. 38% of patients had grade 3+hematologic AE; 72% had grade 3-4 non-hematologic AE. These included: rash, respiratory infection and hypotension in 2 each; atrial fibrillation, diarrhea, edema, dyspnea, and thromboembolism in 1 each. 4 pts had non-objective worsening of their neuropathy. Conclusions: These preliminary results suggest that Ixa-Len-Dex is an effective and tolerable regimen for patients with POEMS syndrome. Clinical trial information: NCT02921893. [Table: see text]

7559 Background: Waldenström macroglobulinemia (WM) is a rare indolent lymphoma commonly treated with rituximab (R)-based therapy. The use of rituximab maintenance (mR) in WM is controversial. We present a case-control study of patients (pts) with WM treated with mR. Methods: Pts evaluated at Mayo Clinic, Rochester with active WM that received mR between 1/2000 & 6/2018 were included. Cases comprised pts who received mR following R-based induction as primary therapy. Cases were matched based on the time of diagnosis in 1:2 ratio with a control group treated with R-based primary induction therapy without mR. Time to event analyses were performed from initiation of R-based induction. Results: Of 776 pts with active WM, 42 (5%) cases received mR and 84 pts were selected as controls. The median follow-up and the proportion of high risk pts were comparable between the two cohorts (Table). Pts in the mR cohort show a trend toward longer time to next therapy (TTNT) and a significantly longer overall survival (OS) compared to the control group (Table). The R-based induction therapies were comparable in the two cohorts (p = 0.6). Median duration of mR was 1.9 yrs (95% CI 1.6-2) and mR was used most frequently every (q) 2 (range 1-6) months. Of the 42 mR pts, 25 (60%) received an R-based combination for induction and 17 (40%) received R monotherapy as induction. Five (12%) pts discontinued mR due to toxicity, infections were reported in 13 pts (31%) during mR therapy and 3 pts (7%) received IVIg infusions for recurrent infections. Conclusions: R-based induction followed by mR demonstrates a longer OS in WM compared to R-treated control population not receiving mR, albeit at a high rate of infections. Despite limitations of a retrospective study, with a heterogeneously treated cohort, these data add to the body of literature supporting Rituximab maintenance. Results from an ongoing randomized controlled trial are awaited. [Table: see text]

7509 Background: Waldenstrom macroglobulinemia (WM) is a rare lymphoma for which scant comparative data exist to guide frontline therapy. Herein, we compare 3 commonly used regimens in WM: R-Benda, DRC, and BDR in frontline setting. Methods: Patients (Pts) with active WM seen at Mayo Clinic between 2000 & 2018 who received R-Benda, DRC or BDR as primary therapy were included in this retrospective study. Response rates were assessed by Consensus Criteria. All time to event analyses were performed from the frontline therapy, using Kaplan-Meier method. Results: The study included 172 pts with active WM (R-Benda, n=67, DRC, n=75, BDR, n=30).The median follow-up for the entire cohort was 3.7 years (y) (95% CI 3.7-3.0). Baseline characteristics, including IPSS, and time to frontline therapy from WM diagnosis were similar across the 3 cohorts. Clinically relevant endpoints are shown in the Table. Hematologic and non-hematologic toxicities were similar across the 3 groups. Grade 3 neuropathy requiring treatment discontinuation was encountered in 13% pts treated with BDR. 56 pts received subsequent salvage therapy [(10% in R-Benda arm, 44% in DRC arm, & 53% in BDR arm]; 29% pts in the R-Benda arm and 30% pts in DRC arm received a PI-based regimen while 69% pts in the BDR arm received alkylator-rituximab based therapy. Conclusions: Outcomes (MRR, TTNT and EFS) with frontline R-Benda are superior in comparison to frontline DRC or BDR in patients with WM. Clinically relevant endpoints are not significantly different with DRC vs. BDR. The toxicity profile across the 3 groups was comparable. [Table: see text]

7020 Background: Histiocytic sarcoma (HS) is a rare and aggressive malignancy of the monocyte/macrophage lineage. There is a paucity of data on treatments and outcomes in HS. Methods: This is a retrospective study of patients with histologically confirmed diagnosis of HS from 2000-2018. Kaplan-Meier and log-rank tests were used to perform overall survival (OS) analyses. Hazard ratios (HR) with confidence intervals (CI) were calculated using Cox-proportional hazards. Results: There were 27 patients in the study (median age 59; range 3-83) and 63% were males. Nine had unifocal involvement and 18 had multifocal disease. Common sites involved were lymph node (50%), soft tissue (40%), bone (36%), and bone marrow (22%). Two of 8 patients had the BRAF-V600E mutation. Next-generation sequencing was performed on 8 patients and showed ≥1 oncogenic alterations (DNMT3A, FLT4, KRAS, NRAS, NUP98, PTCH1, PTPN11, TP53, TSC1, PDGFR, or BRAF genes) as well as a CLIP2-BRAF fusion. The median OS for the cohort was 12 months. Factors associated with worse OS included multifocal disease (OS 10 vs. 125 months, p = 0.03; HR 5.0, CI 1.1-21.8) and marrow involvement (OS 3 vs. 43 months, p = 0.003; HR 8.9, CI 1.7-45.0). Twelve (44%) had surgery with median OS of 42 months (range 1-125). Fifteen had chemotherapy with median OS of 12 months (range 2-67; Table). Conclusions: HS is an aggressive neoplasm, with multifocal disease and bone marrow involvement portending worse outcomes. Most patients have somatic oncogenic alterations involving the MAPK-ERK pathway and other genes. Chemotherapeutic regimens have variable response rates but are not durable. More studies on targeted kinase inhibitors in HS are needed to improve outcomes. [Table: see text]