Geyer, Susan M.

Background: Clonal cytopenias of Undetermined Significance (CCUS) have a higher risk of progression to myeloid neoplasm (MN) compared to idiopathic cytopenias of undetermined significance (ICUS) (Malcovati et al., Blood, 2017). The implementation of flow cytometric (FC) immune-phenotyping and next generation sequencing (NGS) in clinical practice has improved the diagnosis of these entities but the clinical significance and interaction of these abnormal results are still unknown. In this study we investigated predictive factors that play role in survival and progression to MN in patients with ICUS/CCUS. Methods: Patients (Pts) who had undergone evaluation for unexplained cytopenia and had undergone FC and bone marrow morphological assessment between 3/2015-3/2020 at Mayo Clinic Rochester were included. Pts were excluded if a malignant hematological disorder was diagnosed prior to the time of FC. FC included evaluation of the following parameters: Abnormal expression of HLA-DR/CD13, CD2, CD7, CD45, and CD56 on blasts; and abnormal CD13/CD16 expression and side scatter on granulocytic cells. NGS panel up to 2018 included 34 genes, ASXL1, BCOR, BRAF, CALR, CBL, CEBPA, CSF3R, DNMT3A, ETV6, EZH2, FLT3, GATA1, GATA2, IDH1, IDH2, JAK2, KIT, KRAS, MPL, MYD88, NOTCH1, NPM1, NRAS, PHF6, PTPN11, RUNX1, SETBP1, SF3B1, TERT, TET2, TP53, U2AF1, WT1, and ZRSR2; in 2018, BRAF was omitted and 12 genes were added, ANRD26, DDX41, ELANE, ETNK1, KDM6A, MYD88, NOTCH1, RAD21, SH2B3, SRP72, SMC3, and STAG2. Results: Characteristics: Of 490 consecutive pts, 238 (median age 69 years (range 19-92), 66% males) met our inclusion criteria as ICUS. 86 (36%) pts had CCUS (abnormal cytogenetics and/or tested positive for pathogenic mutations on NGS). After a median follow-up of 28 months (95% CI: 20 to 31 months), 21 (25%) patients developed MN and 23 (27%) died during follow-up. Comparing ICUS vs CCUS: upon comparing CCUS pts to ICUS, several factors were found to be significantly different: CCUS pts were older (p= .02); majority male (p= .04), had more abnormal HLA-DR/CD13 (p <.0001), more side-scattered light by FC (p <.0001), more pancytopenia on follow up (p= .02) and more morphologic atypia (<.0001). Overall survival (OS) outcomes in CCUS: Several covariates were significant in univariate models, and model selection was used to generate a risk score based on abnormal CD7, abnormal CD13/CD16, abnormal HLA-DR/CD13, splenomegaly and history of prior chemotherapy or radiotherapy (range: 0 - 4; HR=2.58, [95 CI: 1.69 - 3.94], p<.0001). Risk scores were grouped as low risk (score=0), intermediate risk (score=1), and high risk (score=2+), with estimated 2-yr-OS of 95%, 84%, 40%, respectively (Figure 1). An extended risk score model including NGS factors added ASXL1 and IDH1 mutation status to the previous model (range: 0 - 6; HR=2.72, [95 CI 1.82 - 4.06], p<0.0001). MN-free survival (MNFS) in CCUS: 37 pts either progressed to MN and/or died with a median follow up time for MNFS of 22.4 months. Similar for OS, model selection approaches yielded a composite risk score: splenomegaly, BCOR mutation status, mutation in RAS signaling pathway, abnormal expression of flow markers CD13/CD16, HLA-DR/CD13 or CD7 (HR=3.23, [95 CI: 1.90 - 5.49], p=<0.0001). Risk scores were grouped as low risk (score=0), intermediate risk (score=1), and high risk (score ≥ 2), with estimated 1-yr MNFS of 84%, 74%, and 31%, respectively (Figure 2). Conclusion: CCUS has unique features compared to ICUS. Several factors, including clinical characteristics, immune-phenotyping by FC, and somatic mutations have important impact on risk of progression to MN and on overall survival. Our findings serve as proof-of-concept that such integrated models could help identify CCUS patients at higher risks for progression to MN or death. They can guide treatment accordingly and should be evaluated further. Disclosures Shah: Dren Bio: Consultancy.

361 Background: Assessment of tumor response in extrapancreatic NETs with metastases can be very challenging. Previous studies suggest a high degree of discordance between local and central imaging reviews, which has implications for clinical practice and trial design. Methods: Serial images archived from a randomized phase II trial (A021202) of pazopanib vs placebo in progressive non-pancreatic NETs were evaluated by central review, with real-time review conducted at the time of locally interpreted progressive disease (PD). The primary endpoint of the trial was progression-free survival (PFS) by central review. Discordances between central (Alliance Imaging Core Laboratory) and local (investigator-reported) reviews were assessed. Scan-level and pt-level results across both treatment arms were evaluated. Kappa tests were used to test concordance based on source of review. Results: 151 pts had a total of 724 scans with response adjudication by both local and central RECIST review. Discordance was observed in both directions. Overall, 20% of scans (143/724) had discordant classifications. The most common discordances were: stable disease (SD) on local vs. PD on central review (82/143=57%), and PD on local vs. SD on central review (32/143=22%). On a pt level, 78 of 151 pts (52%) had discordant reviews; 8 had >1 type of discordance. Overall, 30% of pts (N=45) had a determination of PD on central review, but SD or better on local review, potentially resulting in excessive exposure to therapy. In contrast, 20% (N=30) were classified as PD on local read but SD or better on real-time central review (which did not necessarily translate into an abbreviated course of treatment). Cohen’s kappa statistics revealed only moderate concordance between local and central reviewers both at the scan (K=0.48, 95% CI: 0.42 – 0.55) and pt (K=0.41, 95% CI: 0.32 – 0.5) levels, with no significant influence by treatment arm, primary tumor site, tumor functionality, histology, differentiation or primary disease spread. Conclusions: Discordance was observed in both directions, where 30% of pts were potentially kept on study drug too long (based on central read), and 20% would have been taken off study treatment early for local PD were it not for real-time central review. Although this bidirectional discordance did not affect the overall findings of the PFS outcome between arms in the trial, these analyses highlight the high prevalence of discordance, the potential to negatively influence treatment duration in both directions, and the need for more straightforward methods of assessing treatment response in carcinoid. Support: U10CA180821, U10CA180882, U24CA196171; NETRF Investigator Award; https://acknowledgments.alliancefound.org Clinical trial information: NCT01841736.

343 Background: Alliance/CALGB 80802, a randomized phase III trial, evaluated sorafenib plus doxorubicin vs. doxorubicin in pts with HCC and showed no improvement in median overall survival (OS) (HR[95CI] 1.05[0.83-1.31]) or PFS (HR[95CI] 0.93[0.75-1.16]). In HCC surrogacy of tumor response with OS remains controversial, in part due to varying criteria used for response evaluation (e.g., RECIST1.1 and mRECIST). We evaluated the performance of several models to predict OS using pretreatment clinical and radiomic variables. Methods: In CALBG 80802, we segmented all measurable tumor lesions on sequential CT scans. A lesion’s imaging phenotype was deciphered with 23 uncorrelated quantitative imaging features measured at baseline and week (wk) 10 (first follow-up). An OS landmark survival analysis was conducted at wk 10. Patients were randomly assigned (3:1) to training (n = 92) and validation (n = 37) sets. In a training set, 6 random forest predictive models (6 signatures) used features that best predicted OS using 3 sets of variables: radiomics only (n = 23), clinical only (n = 9), radiomics and clinical (n = 32). Two time points (baseline only or baseline + wk 10) were assessed. Each signature's output was an individualized prediction and a continuous value ranging from 0 to 1 (from most to least favorable predicted OS). The primary endpoint was to compare these models' performance to predict OS using error rate (Harrell's concordance-index) in the validation set. Results: Of the 6 training signatures evaluated, the one achieving the highest performance in the validation set was an 8-feature signature combining radiomics and clinical variables measured at two time points (baseline + wk 10) with an error rate of 35.6%. The variables [rank of importance] (table) selected by the signature included baseline clinical features (albumin[1], AFP[2], Child-Pugh[4]), baseline radiomics features (component 17[3], component 1[5], component 9[7], tumor volume[8]) and wk 10 radiomics features (delta tumor volume[6]). Variable delta tumor volume [6] used a more enhanced estimation of tumor burden at baseline and a delta tumor volumetric measurement; compared to RECIST1.1 measurement of percentage change in unidimensional measurement of a subset of target lesions. The four quartiles of the signature were significantly associated with OS (Log-Rank, P < 0.0001). Conclusions: The selected combined radiomic and clinical composite signature provided the best prediction for OS in the 80802 study patients’ population. It is a suggested way forward to go beyond single anatomic measurement techniques such as RECIST or mRECIST. [Table: see text]

325 Background: Alliance/CALGB 80802 randomized phase III trial evaluated DO+S vs. S in pts with aHCC, and showed no improvement in median OS. Multi-drug resistant pathway mitigation by the Ras/Raf/MEK/ERK pathway and bFGF-mediated activation of Raf-1 promotes the formation of antiapoptotic Raf-1 and ASK1 complex, induced by anthracyclines. S efficiently blocks NS5A-recruited c-Raf mediated HCV replication and viral gene expression. Once inhibited by S, VEGF expression of HepG2 may limit HCV cellular entry. Release of Raf-1-Ask-1 dimer and inhibition of Raf-1 via S putatively differ in the presence or absence of DO. We hypothesize treatment with S reduces HCV titer levels (TL) and influence pts’ outcome. Methods: In 80802 HCV pts, TL were evaluated in both arms at baseline and post-baseline at Day 1 of Cycles 2, 3, and every 2 cycles and at progression or discontinuation of therapy. HCV undetectable (HCV-UN) levels were defined as < 50 copies/mL. TL were evaluated in relation to OS and PFS. HCV RNA levels were measured by TaqMan PCR and by genotype. Results: Of 356 pts, 83 were HCV+ with more Black/African American (25/50 = 50%) vs. White (54/239 = 23%) or other race groups (4/67 = 6%) (p < 0.0001). HCV titer data were available on 54 pts (S: 28, DO+S: 26). At baseline, 12 pts (S: 7, DO+S: 5) were HCV-UN, and post-baseline HCV TL did not significantly differ between treatment arms; one patient in each arm went from detectable (HCV-D) to HCV-UN. Post-baseline, 40 pts were HCV-D vs. 14 who were HCV-UN (S+DO: 8, S: 6 pts). Except for the two pts who became HCV-UN, baseline HCV-D vs. HCV-UN titers was similar to that status post-baseline. PFS and OS between HCV-D and HCV-UN both at baseline and post-baseline are delineated in the table. Conclusions: We observed that S did not influence HCV TL. Pts treated with DO+S vs. S had worse PFS if they had HCV-UN, and further that higher levels of HCV titers at baseline were associated with significantly improved PFS. Given the small sample size, these findings warrant further prospective evaluation. Support: U10CA180821, U10CA180882, U24CA196171; Bayer, Bristol-Myers-Squibb, and Sanofi. https://acknowledgments.alliancefound.org . Clinical trial information: NCT01015833. [Table: see text]

Abstract The results from the RATIFY trial (ClinicalTrials.gov: NCT00651261; CALGB 10603) showed that midostaurin combined with standard chemotherapy significantly improved outcomes in patients with FMS-like tyrosine kinase 3 (FLT3)–mutated acute myeloid leukemia (AML), compared with placebo. In this post hoc subgroup analysis from the trial, we evaluated the impact of midostaurin in 163 patients with FLT3-tyrosine kinase domain (TKD) mutations. At a median follow-up of 60.7 months (95% CI, 55.0-70.8), the 5-year event-free survival (EFS) rate was significantly higher in patients treated with midostaurin than in those treated with placebo (45.2% vs 30.1%; P = .044). A trend toward improved disease-free survival was also observed with midostaurin (67.3% vs 53.4%; P = .089), whereas overall survival (OS) was similar in the 2 groups. Patients with AML and NPM1mut/FLT3-TKDmut or core binding factor (CBF)–rearranged/FLT3-TKDmut genotypes had significantly prolonged OS with or without censoring at hematopoietic cell transplantation (HCT), compared with NPM1WT/CBF-negative AMLs. The multivariable model for OS and EFS adjusted for allogeneic HCT in first complete remission as a time-dependent covariable, revealed NPM1 mutations and CBF rearrangements as significant favorable factors. These data show that NPM1 mutations or CBF rearrangements identify favorable prognostic groups in patients with FLT3-TKD AMLs, independent of other factors, also in the context of midostaurin treatment.

e15184 Background: Clinical responses to anti-PD1 immunotherapy in patients with metastatic melanoma (MM) remain challenging to predict. This clinical heterogeneity is also reflected in the tumor-immune microenvironment among patients and within a single tumor lesion. With the emergence of multiplex imaging platforms, defining complex phenotypes at single cell resolution has become possible. Here, we sought to objectively quantify paracrine tumor-immune interactions contributing to the variable clinical responses observed in patients receiving anti-PD1 therapy. Methods: Excisional lymph node (LN) biopsies were obtained from treatment-naïve patients with MM who underwent subsequent anti-PD1 therapy. A single 5µm section of LN tissue was used to assess a 42 analyte panel by multiplex immunofluorescence. From 30 LN samples, 418 fields of view (FOVs) were selected resulting in 14,360 high-resolution images of 4 anatomical subregions: tumor core, tumor-immune interface, tumor infiltrate and adjacent immune stroma. Following image processing, we developed an adaptive classification for tumor-centric cellular neighborhoods (TCCN) to identify and quantify critical paracrine interactions within the tumor-immune microenvironment. Results: Stratification based on responsiveness to anti-PD1 therapy resulted in 4 complete responders (CR) and 12 non-responders (NR) at 12-week follow-up. From 126 FOVs, we defined the cellular composition of 197,865 TCCN across patients based on clinical response and LN subregions. Overall, the percentage of TCCN devoid of any T cells, B cells or macrophages was significantly higher in NR compared to CR irrespective of subregion. However, other markers differentiated TCCN based on subregion. Specifically in CR, tumor core regions were enriched for CD8 T cells, while enrichment for B cells and endothelial cells was demonstrated at the tumor-immune interface. Strikingly, tumor infiltrate regions demonstrate robust immune reactivity with enrichment for M1 polarized macrophages, NK cells and B cells in CR compared to NR. Complete data from the 30 patient cohort across 418 FOVs will be presented. Conclusions: Taken together, this data suggests cellular composition of TCCN across subregions of the LN is dynamic within a single metastatic site. In this small cohort, we introduce a formalized stratification to quantify and classify critical paracrine interactions within the immune-tumor microenvironment with the potential to inform clinical responsiveness to therapy.

TPS2573 Background: Brain metastases, most commonly derived from melanoma, lung and breast cancers, are the most common brain tumor, with approximately 200,000 cases diagnosed annually in the United States. Median survival is on the order of months. For patients with clinically symptomatic brain metastases, approximately half succumb due to intracranial progression. In preclinical work, we demonstrated that brain metastases and primary tumors are often genetically distinct with frequent alterations in the CDK and PI3K pathway (Brastianos, Carter et al. Cancer Discovery 2015). Methods: We are currently accruing to a prospective multi-arm phase II study of CDK, PI3K/mTOR, and NTRK/ROS1 inhibitors in patients with brain metastases harboring alterations associated with sensitivity to these inhibitors (abemaciclib, paxalisib and entrectinib), respectively. Patients with new, recurrent or progressive brain metastases are eligible for this trial. Previously obtained tissue from brain metastases and extracranial sites (primary or extracranial metastases) are screened for the presence of these alterations, and if present in both tumor sites, patients will receive the appropriate corresponding targeted treatment. Screening is carried out with the SNaPshot NGS assay, which is a fully validated clinical test designed and developed at the MGH Center for Integrated Diagnostics. The primary endpoint of response rate (RR) in the central nervous system as per RANO criteria will be evaluated separately for each inhibitor, stratified by histology within each arm. There will be 21 evaluable patients assigned to each of the CDK and PI3K inhibitor and tumor type cohorts (breast, lung and other) and 10 patients assigned to the NTRK/ROS1 inhibitor cohort (lung) for a total of 136 evaluable patients. Although current systemic therapy for brain metastases is often ineffective, we hypothesize that targeted therapies will demonstrate efficacy in patients harboring the appropriate mutations. This study represents a novel individualized therapeutic approach in brain metastases, a disease with a critical need for effective therapy. Support: U10CA180821, U10CA180882, https://acknowledgments.alliancefound.org ; Genentech, Kazia Therapeutics Limited, Eli Lilly; Clinical trial information: NCT03994796 .

2502 Background: Patients with progressive or recurrent meningiomas have limited treatment options. Clinical trials of systemic therapies for meningiomas have failed to demonstrate benefit. FAK inhibition has a synthetic lethal relationship with NF2 loss. Given the predominance of NF2 mutations in meningiomas, we evaluated the efficacy of GSK2256098, a FAK inhibitor, as part of the first genomically-driven phase II study in recurrent or progressive grade I-III meningiomas. Methods: Eligible patients (pts) whose tumors screened positively for NF2 mutations were treated with GSK2256098 750mg po bid until progressive disease in 2 separate cohorts: grade I or II/III meningiomas. Two co-primary endpoints were used: progression-free survival at 6 months (PFS6) and response rate (RR) by Macdonald criteria; per study design, the trial would be declared positive if either endpoint was met. RR was evaluated across the overall cohort; PFS6 was evaluated within each subgroup. Historical benchmark data was obtained from Kaley et al. Neuro Oncol 2014. In the grade I group, 12 evaluable pts provided >79% power to detect a PFS6 rate >65% (vs. null hypothesis of 25%; alpha=0.014). In the grade II/III group, 24 evaluable pts provided >85% power to detect a PFS6 >41.5% (vs. null 15%; alpha=0.02). The threshold for promising results for PFS6 was: 7+/12(grade I) and 8+/24(grade II/III) pts. For RR, 36 evaluable pts provided >94% power to detect RR >20% (vs. null 2.5%; alpha= 0.012). Results: Of 322 pts screened for all mutation cohorts of the study, 36 eligible and evaluable pts with NF2 mutations were enrolled. Across all grades, one pt had a partial response and 24 had stable disease as best response to treatment. In Grade I pts, the observed PFS6 rate was 83% (10/12 pts; 95% CI: 52-98%). In Grade II/III pts, the observed PFS6 rate was 33% (8/24 pts; 95% CI: 16-55%). The study met PFS6 efficacy endpoint both for the Grade I and the Grade II/III cohorts. Treatment was well tolerated. Only 7 patients had a maximum grade-3 adverse event that was at least possibly related to treatment; toxicities across these pts included: proteinuria (2), rash (1), pain (1), ALT (1), AST (1), cholecystitis (1), hypertriglyceridemia (1), apraxia (1), and lymphopenia (1) with no grade 4 or 5 events. Conclusions: GSK2256098 had excellent tolerability andresulted in an improved PFS6 rate in pts with recurrent or progressive NF2-mutated meningiomas. Trial endpoint was met. FAK inhibition warrants further evaluation in this patient population. Support: U10CA180821, U10CA180882; https://acknowledgments.alliancefound.org Clinical trial information: NCT02523014 .

Abstract Purpose: Lenalidomide (CC-5013) is an analogue of thalidomide and a lead clinical compound in a new group of drugs called IMiDS® which have immunomodulatory properties. Lenalidomide has shown promising results in relapsed refractory myeloma. It has a markedly different side-effect profile compared to thalidomide, with significantly fewer non- hematologic adverse events; myelosuppression, especially neutropenia, is the most common toxicity. We report the results of a phase II trial using the combination of lenalidomide plus dexamethasone (Rev/Dex) as initial therapy for newly diagnosed multiple myeloma. Patients and Methods: 34 patients (23 male and 11 female) were enrolled. Lenalidomide was given orally 25 mg daily on days 1–21 of a 28-day cycle. Dexamethasone was given orally at a dose of 40 mg daily on days 1–4, 9–12, 17–20 of each cycle. Patients were allowed to go off treatment after 4 cycles of therapy to pursue stem cell transplantation, but treatment beyond four cycles was permitted at the physician’s discretion. For patients continuing therapy beyond 4 months, the dose of dexamethasone was reduced to 40 mg on days 1–4 of each cycle. Objective response was defined as a decrease in serum monoclonal (M) protein by 50% or greater and a decrease in urine M protein by at least 90% or to a level less than 200 mg/24 hours, confirmed by two consecutive determinations at least 4 weeks apart. Sub-classification as very good partial response (VGPR) required in addition to criteria for partial response, &gt;=90% reduction in serum M protein, 24 hour urine M protein less than or equal to 100 mg, and 5% or fewer plasma cells on bone marrow examination. All patients received aspirin (81 mg or 325 mg daily) as prophylaxis against DVT. Results: The median age was 64 years (range, 32–78). All patients were evaluable for response and toxicity. Thirty-one of 34 patients (91%) achieved an objective response to therapy, including 2 patients (6%) achieving a complete response (CR) and 11 patients (32%) achieving very good partial response. Of the 3 patients not achieving an objective response, two met criteria for minor response and one had stable disease. Responses were rapid; the median time to response was 1 month. Adequate stem cells (&gt;3.0 million CD34 cells/kg body weight) were obtained in all patients who proceeded to autologous stem cell transplantation. Forty-seven percent of patients experienced grade 3 or higher non-hematologic toxicity, most commonly fatigue (15%), muscle weakness (6%), anxiety (6%), pneumonitis (6%) and rash (6%). One patient died on study, and this was attributed to infection unrelated to therapy; the patient had stopped all therapy for over a month before the fatal infection occurred. One patient developed a pulmonary embolism, but recovered with therapy; no other patient developed deep vein thrombosis or pulmonary embolism. Conclusion: Rev/Dex is highly active and well tolerated in the treatment of newly diagnosed multiple myeloma with overall responses in over 90% of patients including complete and very good partial responses in 38%. Two large cooperative group trials are currently testing Rev/Dex as initial therapy for multiple myeloma in the United States.

Abstract Background. The strongest established prognostic factors for follicular lymphoma are age and clinical factors. Biologic studies suggest a major role for the host immunologic environment in follicular lymphomagenesis, which is in part determined by host genetic background. Cytokines are key regulators of immune function and regulation, are highly polymorphic, and have been implicated in lymphoma etiology and prognosis. We evaluated the hypothesis that inherited variability in cytokine and related immune genes impact overall survival in follicular lymphoma. Methods. We genotyped 73 single nucleotide polymorphisms (SNPs) from 44 candidate cytokine and immune genes in 278 follicular lymphoma patients who participated in a population-based case-control study conducted from 1998–2000 in the Detroit, Iowa, Los Angeles and Seattle SEER (Surveillance, Epidemiology and End Results) cancer registries. Baseline clinical data and survival through early 2005 were obtained from cancer registry files. Cox proportional hazards analysis was used to estimate hazard ratios (HR) and corresponding 95% confidence intervals for the association between individual SNPs and overall survival, adjusting for age, demographic and clinical factors. We also used parallel modeling strategies to identify the best summary multi-SNP risk score to predict survival, and applied these results in a time-dependent receiver-operator characteristics (ROC) analysis. Results. The median age at diagnosis was 57 years (range, 25–74), and 59 (21%) of the patients died during follow-up, with a median follow-up of 59 months (range, 27 – 78 months) for surviving patients. In multivariate modeling, SNPs in IL8 (rs4073; HRTT=2.14, 1.26–3.63), IL2 (rs2069762; HRGT/TT=1.80, 1.06–3.05), IL12B (rs3212227; HRAA/CC=1.83, 1.06–3.06), and IL1RN (rs454078; HRAA=1.93, 1.11–3.34) were the strongest and most robust predictors of survival. A summary score of the number of deleterious genotypes from these four genes was strongly associated with survival (p=1.4 × 10−5) after accounting for demographic and clinical variables (HR=2.06 per deleterious genotype, 1.52–2.79). A combination of the four SNPs and the demographic and clinical risk scores was strongly associated with survival (p=1.8 × 10−11); the 5-year Kaplan Meier survival estimates were 96% (93%–100%), 72% (62%–83%) and 58% (48%–72%) for low, intermediate, and high risk groups respectively. In a time-dependent ROC analysis the three risk groups had an area under the curve (AUC) of 0.83 at 72 months of follow-up (95% CI 0.72–0.93). Conclusion: Host genetic variability in immune genes, particularly IL8, IL2, IL12B, and IL1RN, individually and particularly in combination, was associated with overall survival in follicular lymphoma after accounting for demographic and clinical factors. Host immunogenetics is a promising class of prognostic factors in follicular lymphoma that warrants further evaluation.