Goyal, Gaurav

Introduction: The landmark VE-BASKET trial demonstrated that Erdheim-Chester disease (ECD) patients with the BRAF-V600E mutation can be effectively treated with vemurafenib 1920 mg/day. However, all patients required dose reductions due to adverse effects. The efficacy of low dose BRAF-inhibitors is not well established in ECD. Further, as Langerhans cell histiocytosis (LCH) also harbors BRAF-V600E mutations in 50-60% of patients, BRAF-inhibitors may be effective in this disease as well. In this study, we evaluated the efficacy of low dose BRAF-inhibitors (vemurafenib and dabrafenib) in the treatment of ECD and LCH. Methods: We conducted a retrospective study of ECD and LCH patients who were seen at our institution from January 1998 to July 2018. All patients had a diagnosis of ECD and LCH determined by clinical criteria in conjunction with histopathologic findings. Based on the standard doses approved for malignant melanoma and ECD, patients were categorized into the low dose BRAF-inhibitor group if they were treated with vemurafenib < 960 mg/day or dabrafenib ≤ 150mg/day at any point in time. We used a simple response criteria that defined clinical progressive disease (PD) as worsening of symptoms attributed to ECD/LCH or radiologic PD as a progression or worsening of proven or suspected lesions due to ECD/LCH. The minimum duration for symptom improvement to be considered a response was set at 3 months. Results: A total of 89 ECD patients and 186 LCH patients were identified. Within the ECD cohort, 24 of 44 (55%) patients who were tested had the BRAF-V600E mutation. Eight patients were included in the low dose BRAF-inhibitor group. The median age at diagnosis was 57 years (range 37-74) and 5 (63%) were male. The most common areas of involvement included bone (88%), cardiovascular system (63%), kidneys (63%), and brain parenchyma (50%). The median time of follow up was 66 months (range 23-165) and the median time on low-dose BRAF-inhibitor was 10 months (range 1-27) [Table 1]. Three patients had a starting dose of vemurafenib 1920 mg/day, 4 had 960 mg/day, and 1 had 480 mg/day. All patients required dose reductions and 50% of the patients ultimately discontinued vemurafenib due to side effects. Side effects included fatigue, pruritus, nausea, facial swelling, blisters, papillomas, and/or subcutaneous nodules. Four patients were able to remain on low-dose vemurafenib for a median follow up time of 24.5 months (range 12-28) with ongoing response and no signs of clinical or radiologic PD. Within the LCH cohort, 18 of 31 tested (58%) patients had the BRAF-V600E mutation. Four patients were included in the low dose BRAF-inhibitor group. The median age at diagnosis of this cohort was 43 years (range 34-69) and 2 (50%) were male. Areas of involvement included bone (100%), brain parenchyma (hypothalamus/optic stalk and pons; 50%), and skin (25%). The median time of follow up was 31 months (range 21-46) and the median time on low-dose BRAF-inhibitor was 4 months (range 3-24) [Table 2]. Two patients had a starting dose of vemurafenib 960mg/day. The patients with brain parenchymal involvement had a starting dose of dabrafenib 150mg/day or 100mg/day. All patients taking vemurafenib 960mg/day required dose reductions and one patient discontinued treatment due to skin blistering in her feet. In the patients taking dabrafenib, no side effects have yet been reported. 3 patients had an ongoing response and did not have clinical or radiologic PD. Patient #10 however, had clinical and radiologic PD after being on vemurafenib 720mg/day for 22 months. Conclusion: Our study suggests a potential role for lower doses of BRAF-inhibitors in ECD and LCH patients harboring BRAF-V600E mutations. Dabrafenib was found to be particularly efficacious and well-tolerated in LCH involving the brain parenchyma. However, patients who undergo dose reductions should be closely monitored due to the risk of disease progression. Careful balance of toxicities and efficacy is needed for optimizing patient outcomes with targeted therapies. Disclosures Bennani: Adicet Bio: Other: Advisory board; Kite Pharma: Other: Advisory board; Purdue Pharma: Other: Advisory board; Purdue Pharma: Other: Advisory board; Seattle Genetics: Other: Advisory board; Purdue Pharma: Other: Advisory board; Adicet Bio: Other: Advisory board; Kite Pharma: Other: Advisory board; Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Research Funding; Adicet Bio: Other: Advisory board; Bristol-Myers Squibb: Research Funding; Kite Pharma: Other: Advisory board; Seattle Genetics: Other: Advisory board; Seattle Genetics: Other: Advisory board. OffLabel Disclosure: Vemurafenib and dabrafenib for Langerhans cell histiocytosis. Vemurafenib dosage for Erdheim-Chester disease is less than the approved dose of 960mg every 12 hours.

Introduction Langerhans cell histiocytosis (LCH) is an uncommon histiocytic disorder which is now categorized as a hematopoietic neoplasm. Most treatment and outcomes data in LCH are derived from pediatric studies, and there is a lack of FDA-approved treatment options for adult LCH. There is some evidence that cladribine may be toxic to monocytes and monocyte-derived dendritic cells. In this study, we report the efficacy of cladribine in adult LCH patients seen at our institution. Methods We retrospectively reviewed the charts of all LCH patients seen at our institution between 1998 and 2018. Where necessary, the radiological images and histopathological slides were reviewed by an expert radiologist and pathologist. Since prospective uniform response assessment was not performed, we utilized the clinical documentation and radiological reports to assess the overall response rate (ORR). All time to event analyses were performed from the time of cladribine initiation. Results We included a total of 37 adult LCH patients in the study. The median age at diagnosis for this cohort was 35 years (range, 21-76), and 51% were males. Although 31 (84%) patients had multi-system disease, all patients had more than one LCH lesion (multifocal). Most commonly involved organs were bone (65%), lung (60%), skin (38%), lymph nodes (30%), and pituitary/hypothalamus (27%). BRAF-mutational analysis was performed in 13 patients, with 7 (54%) demonstrating the presence of BRAF-V600E mutation. Cladribine was administered as first line therapy in 22 (59%) patients and subsequent line treatment in 15 (41%). Of the 15 patients who received cladribine in subsequent line, surgery (n=3), radiation (n=3), steroids (n=3), antibiotic with inhaled steroids (n=1), vinblastine (n=3), topical nitrogen mustard cream (n=1) and vemurafenib (n=1) were the treatments utilized before the initiation of cladribine. Two patients received the drug more than once during the course of their disease. The dosing of cladribine for all patients was based on one of the two intravenous regimens (0.14 mg/kg for days 1-5 every 28 days or 5 mg/m2 for days 1-5 every 28 days). The median follow-up for the entire cohort was 4.5 years (95% CI:2-7) and the treatment outcomes are shown in Table 1. Median number of cycles of cladribine administered was 1.5 (range, 1-9). Clinical/radiographic responses were noted in 29 (78%) patientsORR was 78%, with 24% complete responses and 54% partial responses (PR). Responses were seen in various disease sites: lung nodules/infiltrates (13/29, 45%), bone (12/29, 41%), lymph nodes (8/29, 28%), skin (3/29, 10%), pituitary/hypothalamus (4/29, 14%). Eight (22%) patients did not respond and had progressive disease (PD)- cystic/bullous lung disease (n=2), skin (n=2), abdominal/peritoneal lymph nodes (n=2), and hypothalamus (n=3).The treatment was well tolerated, with grade 3 or above adverse effects seen in three patients: two with lymphopenia requiring dose delays and one with congestive cardiac failure leading to drug discontinuation. After initial disease response, PD was seen in three patients. 89%, 78%, 64% of those who responded initially maintained their responses at years 1, 3, and 5, respectively (Table 1). The 5-year progression free survival (PFS) was 55% for the entire cohort. BRAF-status was evaluated on 13 of 37 patients in the entire cohort (35%): BRAFV600E positive [n=7 (53%)] and WT [n=6 (46%)]. Of the 7 patients who had BRAFV600E mutation, responses were seen in 71%, while 100% of those without BRAFV600E achieved a response (p=0.09). At the time of last follow-up, 9 patients (24%) were dead. Of those, cause of death were available on 5 patients; due to LCH (n=1), stroke (n=1), gastrointestinal hemorrhage (n=1), acute myeloid leukemia (n=2). Conclusion In our study, cladribine monotherapy yielded a high ORR, with the majority of patients achieving a PR. The responses were durable with a small risk of subsequent disease relapse. Responses were seen irrespective of the presence of BRAFV600E mutation. Cladribine was well tolerated overall, and may be considered a potential therapy for adult LCH patients. Disclosures Vassallo: Sun Pharmaceuticals: Research Funding; Pfizer: Research Funding; Bristol Myers Squibb: Research Funding; Sun Pharmaceuticals: Research Funding; Bristol Myers Squibb: Research Funding. OffLabel Disclosure: Cladribine for langerhans cell histiocytosis

Introduction Histiocytic neoplasms are rare disorders of the monocyte-macrophage-dendritic cell lineage that pose significant management challenges to the clinicians. Over the last five years, there has been emerging data on the role of MAPK/ERK pathway (RAS-RAF-MEK-ERK) in their pathogenesis. In this study, we report the molecular alterations among patients with histiocytic neoplasms seen at our institution. Methods We pursued target-capture next generation sequencing (NGS) on tissue specimen of patients with various histiocytic neoplasms- Erdheim-Chester disease (ECD), Langerhans cell histiocytosis (LCH), Rosai-Dorfman disease (RDD), histiocytic sarcoma (HS), and Langerhans cell sarcoma (LCS). We used three NGS platforms, Tempus® xO (1,714 genes), Tempus® xT (596 genes), or Foundation One® CDX (324 genes). All platforms used formalin-fixed paraffin-embedded tumor tissue specimens for detection of substitutions, insertion and deletion alterations, and copy number alterations, and gene rearrangements. The Tempus assays also utilized matched blood or saliva samples for germline DNA sequencing in addition to whole-transcriptome RNA sequencing. The tumor cellularity threshold for pursuing RNA sequencing was 30% so the test was not pursued specimens for lower cellularity. Results We included 31 cases with histiocytic neoplasms in this study. The disease distribution was as follows: ECD (n=6), LCH (n=7), RDD (n=12), ECD-RDD overlap (n=3), HS (n=2), and LCS (n=1). Among the 13 patients with ECD and LCH, BRAF-V600E mutations were found in 8 (62%) cases. We found several novel DNA alterations in this study in all disease groups: ECD (BRAFV471F), LCH (MAP2K1 in-frame deletion), and RDD (frameshift mutations of DNMT3A, SMARCA4, KMT2A, and CDC73 truncation). In one LCH patient without any DNA alterations, we found MAPK1 and MAP2K1 overexpression on RNA sequencing. We also had two cases with HS, both of which were found to have KRAS exon 3 mutations. One of these cases had concomitant JAK2V617F+ myelofibrosis and the tissue specimen for HS demonstrated TET2 and SRSF2 mutations as well. Our cohort included one patient with multifocal lymph node LCS that demonstrated NRAS and TP53 mutations, who did not respond to MEK-inhibitor therapy. Alterations in epigenetic regulators (TET2, DMNT3A, KMT2A, ASXL1) were found in 5 (16%), potentially suggesting clonal hematopoiesis in a subgroup of histiocytosis. Conclusions Histiocytic neoplasms demonstrate diverse somatic oncogenic alterations. In our study, we noted several novel alterations beyond the MAPK-ERK pathway in RDD that may point toward other potentially pathogenic mechanisms for these rare disorders. In cases where the DNA sequencing does not reveal pathogenic alterations, transcriptome analysis may aid in the diagnosis and management. OffLabel Disclosure: Trametinib use for Langerhans cell sarcoma

Purpose: Langerhans cell histiocytosis (LCH) is a rare histiocytic disorder that presents with a wide spectrum of clinical diseases, ranging from single-organ lesions to systemic disease. Although previously thought of as an immune disorder, LCH was reclassified as an inflammatory myeloid neoplasm in the 2016 Histocyte Society classification after discovery of BRAF V600E or MAP2K1 gain-of-function mutations and evidence of clonality in most LCH patients. In this revised classification, LCH was divided into single-system LCH, pulmonary LCH, or multisystem LCH. However, there is a lack of data on clinical features and outcomes in the subgroup of "unifocal" non-pulmonary LCH in adults. In this study, we sought to address the gaps in knowledge for unifocal adult LCH utilizing our institution's experience over 20 years. Methods: We retrospectively reviewed the medical records of 189 adult patients (defined as >18 years old at diagnosis) with histopathologically confirmed LCH who were seen at our tertiary referral center between 1997 and 2018. Of these, 44 met criteria for unifocal LCH at diagnosis after careful exclusion of other sites of disease involvement. Results: We included 44 adult patients with unifocal LCH at diagnosis, with median age 42 years (range 19 to 88) and 55% males. 84% were Caucasians and 50% were smokers. Most commonly involved disease sites included bone (43%), skin (25%), pituitary (14%), and gastrointestinal (11%), with common presenting symptoms of head pain/swelling (25%), skin rash (20%), abdominal pain/diarrhea (11%), and diabetes insipidus (9%). Resection/excision was the most common first line therapy in 24 patients (63%); none had local recurrence and 3 patients developed recurrence at a new site. Radiation was the second most common therapy in 6 patients, with an overall response rate of 83%; none had local recurrence and 1 patient had recurrence at a new site. Other less common first-line treatments included resection followed by radiation (2), topical immunosuppression (2), dexamethasone (1), cladribine (1), smoking cessation (1), and observation (1) (Table 1). Cladribine used as first-line therapy for pituitary LCH resulted in progressive disease, but cladribine used as second-line therapy in 2 cases (including one who had progressed to multisystem disease) resulted in partial remission with no further recurrence in both cases. Patients were followed for a median of 3.8 years (range 0.1 to 18.8), with 5 patients lost to follow-up. By time of last follow-up, 11 (28%) had developed recurrence: 1 had local recurrence, 5 developed disease at a new site within the same system (skin or bone), and 5 developed multisystem disease (Figure 1). Median time to recurrence was 2 years (range 0.2 to 6.6). 2 out of 5 patients tested for BRAF had a V600E mutation, both of whom had isolated unifocal bone disease and remained in complete remission following resection at time of last follow-up. Median overall survival (OS) from time of diagnosis was not reached and overall 5-year OS was 94%. 3 patients died, only 1 of progressive LCH. Conclusion: In our study, most patients with unifocal adult LCH achieved a complete remission with surgical resection or local radiation. None of the patients treated with resection or radiation developed local recurrence, but around 1 in 5 developed distant recurrence within 5 years. However, the overall prognosis was very good, and none of the patients in the cohort progressed to "high-risk" organ (liver, spleen, or bone marrow) involvement or pulmonary involvement. Further studies are warranted to assess the role of MAPK-ERK mutations in the prognosis of unifocal LCH. Disclosures Bennani: Seattle Genetics: Other: Advisory board; Adicet Bio: Other: Advisory board; Adicet Bio: Other: Advisory board; Adicet Bio: Other: Advisory board; Kite Pharma: Other: Advisory board; Kite Pharma: Other: Advisory board; Kite Pharma: Other: Advisory board; Purdue Pharma: Other: Advisory board; Seattle Genetics: Other: Advisory board; Purdue Pharma: Other: Advisory board; Seattle Genetics: Other: Advisory board; Purdue Pharma: Other: Advisory board; Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Research Funding; Bristol-Myers Squibb: Research Funding. Vassallo:Sun Pharmaceuticals: Research Funding; Sun Pharmaceuticals: Research Funding; Pfizer: Research Funding; Bristol Myers Squibb: Research Funding; Bristol Myers Squibb: Research Funding.

BackgroundPrior studies in oncology have shown that a higher annual facility patient volume is associated with reduced mortality. Because classic Hodgkin lymphoma is uncommon but highly curable, this study used the National Cancer Database (2003‐2014) to analyze whether such a relationship exists for this disease.MethodsThe facilities were classified by quartiles, and random intercepts were used to account for clustering of patients within facilities. A Cox regression model was used to determine the volume‐outcome relationship.ResultsThere were 47,633 patients with classic Hodgkin lymphoma treated at 1310 facilities. The first quartile (Q1), which included 58.4% of the facilities, treated 3 or fewer patients per year, whereas the fourth quartile (Q4), which included 5.9% of the facilities, treated more than 9 patients per year. Compared with the patients treated at Q4 facilities, those treated at lower quartile facilities had a higher risk of death (hazard ratio for the third quartile [HR], 1.19; 95% confidence interval [CI], 1.1‐1.29; HR for the second quartile, 1.28; 95% CI, 1.19‐1.38; HR for Q1, 1.29; 95% CI, 1.2‐1.39) after adjustments for all other factors (P < .0001). Compared with facilities treating 10 patients per year, facilities treating 40 patients per year had approximately 27% lower overall mortality rates.ConclusionsPatients with classic Hodgkin lymphoma treated at high‐volume centers had lower overall mortality than those treated at lower volume centers. Because this is a highly curable malignancy, such differences may suggest a benefit from referral to higher volume facilities or the emulation of their care models.

Abstract Introduction: Chronic lymphocytic leukemia (CLL) is the most common type of adult leukemia, with ~21,000 estimated new cases in 2018. Prior retrospective studies have suggested an increased risk of second primary malignancies (SPMs) in CLL patients. Population-based studies on the risk of SPMs in CLL are limited, especially in the last decade with improvements in prognostic and therapeutic tools over the last decade. As the survival of CLL patient improves, it may lead to more survivors who are at risk of developing SPMs. In this study, we sought to evaluate the risk of development of SPMs among CLL patients diagnosed from 2000-2014. Methods: We used the SEER 18 registries for the calculation of risk of SPMs and included CLL cases that were confirmed histologically between 2000-2014 (https://seer.cancer.gov/). SPMs diagnosed within 2 months of primary CLL diagnosis were excluded. Time to SPM was calculated by subtracting second malignancy survival/follow-up time from CLL survival/follow-up time. The SEER*Stat Multiple Primary-SIR tool was used to calculate SIRs for secondary malignancies by comparing these patients' subsequent cancer experience with the number of cancers that would be expected based on incidence rates for the general U.S. population. These analyses were adjusted for age, gender, race, and year of CLL diagnosis. Multivariate logistic regression was performed to identify factors associated with development of SPM. Results: The study cohort included 46,164 patients with CLL. After a median follow up of 50 months (range 1-179), 5220 (11.3%) patients developed a total of 5,738 subsequent malignancies. As compared to that of general population, CLL patients had a higher risk of developing SPMs (SIR: 1.40 [95%CI:1.37-1.44]) and the risk was much higher for hematologic malignancies (SIR: 2.63 [95%CI:2.47-2.80]) as compared to solid organ malignancies (SIR: 1.25 [95%CI: 1.22-1.29]). In addition to known common SPMs in CLL (lymphoma, melanoma, lung cancer, and prostate cancer), there was an elevated risk of developing acute lymphoblastic leukemia (SIR 5.43), chronic myeloid leukemia (SIR 2.18), thyroid cancer (SIR 2.09), and kidney cancer (SIR 1.70) (Table). Out of the 5220 patients who developed SPMs, 437 (8.3%) patients developed two subsequent second primary malignancies, and 81 (1.5%) patients developed > 2 subsequent primary cancers, which was significantly more than the endemic rate (SIR, 1.40; p <.05). Of the 5738 SPMs, 1095 (19%) occurred in 2-11 months, 2822 (49%) in 1-5 years, 1499 (26%) in 6-10 years and 321 (6%) beyond 10 years of CLL diagnosis (Figure). On logistic regression, males had higher odds of developing SPMs than females (OR: 1.46 [95% CI: 1.38-1.56], p<0.0001) and the patients diagnosed with from 2000-2007 had higher odds of developing SPMs as compared to those diagnosed from 2007-2014 (OR: 2.28 [95%CI: 2.15-2.42], p<0.0001]. The risk of developing SPM did not differ based on the age, race and between the patients who received first line therapy and no initial therapy. CLL patients who developed SPMs had significantly less median overall survival as compared to that of patients who did not develop SPMs (93 vs 109 months, p<0.05). Conclusion: In this large population-based study, CLL patients had an elevated risk of developing second primary hematologic and solid malignancies. The specific types of SPMs were varied, ranging from common ones such as lymphoma, lung cancer, prostate cancer, to uncommon ones such as thyroid cancer, kidney cancer, and chronic myeloid leukemia. The patients who were diagnosed after 2007 had a lower risk of developing SPMs as compared to those diagnosed before. There is a need for studies evaluating immunological repertoire of CLL and its impact on development of SPMs. Knowledge of these SPMs may help physicians with their early detection. Disclosures No relevant conflicts of interest to declare.

Abstract Background Hodgkin lymphoma is a rare hematological malignancy, with 8,500 new cases per year in the United States. Prior studies in oncology have shown that higher patient volume, whether at the treatment facility or provider level, is associated with reduced mortality and improved overall survival (OS). We used a national oncology data set to test our hypothesis that a volume-outcome relationship may also exist in classical Hodgkin lymphoma. Methods Using the National Cancer Data Base (NCDB), we identified patients diagnosed with classical Hodgkin lymphoma between 2003 and 2014. The NCDB is a nationwide oncology outcomes database for ~70% of newly diagnosed cases from more than 1,500 accredited cancer programs in the United States and Puerto Rico. We classified the facilities by quartiles (Q; mean patients with HL treated per year): Q1: < 3.19, Q2: 3.2 to 5.0, Q3: 5.01 to 9.19, and Q4: ≥9.2. Our primary outcome of interest was all-cause mortality. We used random intercepts to account for clustering of patients within facilities and a Cox regression model to determine the volume-outcome relationship, adjusting for demographic (sex, age, race, ethnicity), socioeconomic (income, education, insurance type), geographic (area of residence, treatment facility location, travel distance), and comorbid (Charlson-Deyo score) factors, as well as year of diagnosis. Kaplan-Meier analysis was performed to examine the impact of patient volume (by quartile) on overall survival. Results There were 47,633 patients with classical Hodgkin lymphoma treated at 1,310 facilities. The median age at diagnosis was 40 years, and 54.2% were men. The median annual facility volume was 2.7 patients per year (range, 1 to 42.8). The distribution of facilities according to patient volume was: Q1: 58.4%, Q2: 22.4%, Q3: 13.3%, and Q4: 5.9%. After a median follow-up of 58 months, the highest volume quartile (Q4) had significantly higher 5- and 12-year overall survival rates compared to Q1-Q3 (Table 1). Overall survival by quartile is depicted as a Kaplan-Meier curve (Figure 1). Compared to the patients treated at Q4 facilities, those treated at lower-quartile facilities had a higher risk of death (Q3 hazard ratio [HR], 1.18 [95% CI, 1.10 to 1.27]; Q2 HR, 1.21 [95% CI, 1.13 to 1.30]; Q1 HR, 1.19 [95% CI, 1.11 to 1.28]) after adjustment for the sociodemographic factors discussed in our methods. Multivariable analysis showed that facility volume as a continuous variable was independently associated with all-cause mortality (Figure 2) (P<0.0001). Compared with facilities treating 10 patients per year, facilities treating 20, 30, and 40 patients per year had approximately 10%, 17%, and 23% lower overall mortality rates. Conclusions Patients treated for classical Hodgkin lymphoma at higher-volume facilities had a lower risk of mortality compared with those treated at lower-volume facilities. This adds to the growing body of evidence that a volume-outcomes relationship exists in some of the less common hematologic malignancies. Further research is needed to ascertain whether such differences in survival are related to provider-level or facility-level attributes, and whether patients with Hodgkin lymphoma will benefit from referral to high-volume centers. Disclosures No relevant conflicts of interest to declare.

Abstract Background: The incidence of multiple myeloma (MM) in the US is increasing among non-Hispanic (NH) White males and females as well as NH Black males (Costa LJ, Blood Advances 2017). However, more specific incidence studies accounting for geographic and age subgroups are limited. There is also a growing concern that incidence of many cancers is increasing in the younger population. Utilizing the Surveillance, Epidemiology, and End Results Program (SEER), we investigated the trends in MM incidence in the US according to demographic and geographic subgroups with a focus on the young adults. Methods: Incidence rates (case/100,0000) were calculated using SEER*Stat and 2000-2015 data from SEER-18 registries age-adjusted to the U.S. 2000 standard population. We calculated the annual percentage change (APC) of incidence rates according to age groups and stratified by sex, race, and registry. Age at diagnosis was analyzed in 10-year intervals starting at 20 years. All analyses used ICD-O-3 codes 9732/3 with microscopically confirmed MM. Results: There were 69,613 MM patients included in the analysis. The mean age at diagnosis was 68 years and decreased over time from 68.5 years in 2000 to 67.6 years in 2015. Men comprised 55.5% of the population. Patients <50 years constituted 7.9% of the population with 6.6% between 40-49 years. The incidence significantly (all p values <0.01) increased from 2000-2015 for the entire cohort (incidence 6.9-9.5; APC 1.1) and for males (8.6-9.5; 1.1) and females (5.7-6.3; 0.8). The highest increase in incidence among the age groups (Figure) was in 40-49 years (1.9-2.7; 2.1). When analyzing the trends for age groups stratified by sex, women ages 40-49 years had the highest increase in incidence (1.6-2.6; 2.4). The APCs of SEER-18 registries stratified by age and sex are reported in the Table. The highest APCs (>3.0) were observed in the registries of Atlanta, Greater Georgia, Hawaii, and New Jersey. When the SEER-18 registries were further stratified by race, white men ages 40-49 years in Seattle and New Jersey had APCs of 5.5 and 2.9 respectively, while Black women ages 40-49 years in Greater Georgia had an APC of 3.3. Only 3 groups of individuals had a significant decline in the incidence: Asian women ≥70 years in Los Angeles (APC -6.4), White women ≥70 years in Los Angeles (APC -1.9), and men 50-59 years in San Jose (APC -1.5). Conclusions: The overall incidence of MM is increasing in the US with the highest increment among young adults between the age groups 40-49 years. We observed geographic and demographic differences in the incidence rates, which may reflect genetic and environmental influences. Interestingly, a few geo-demographic subgroups had a decline in the incidence. Further research is needed to determine the reasons behind the observed trends. Disclosures Kapoor: Celgene: Research Funding; Takeda: Research Funding.

Abstract Introduction Histiocytic neoplasms are rare hematological malignancies that have protean clinical manifestations and can pose significant management challenges. Recently, vemurafenib was approved by the US-FDA for treatment of BRAF-V600-mutant Erdheim-Chester disease (ECD). However, there is a lack of FDA-approved therapies for other histiocytic neoplasms such as Langerhans cell histiocytosis (LCH) and Rosai-Dorfman disease (RDD). Over the last 5 years, immune checkpoint inhibitors such as programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors have shown significant improvement in outcomes among patients with several hematological and solid organ malignancies. In order to identify appropriate treatment candidates for these therapies, predictive biomarkers have been developed in various cancers. Evidence from solid tumors has suggested a favorable response to checkpoint inhibitor therapy with higher tumor mutational burden (TMB), defined as the number of mutations within a tumor genome. Next generation sequencing (NGS) of various tumors has shown an association between TMB of < 5 mutations/megabase (mut/Mb) to be associated with an absence of benefit from checkpoint inhibitors. In addition, high levels of PD-1/PD-L1 expression and microsatellite instability (MSI) are also correlated with response to therapy. The latter may be a result of somatic or germline alterations in DNA mismatch repair genes. In this study, we report the results for these biomarkers using NGS in patients with histiocytic neoplasms. Methods We utilized TempusTM NGS platform to analyze the tissue specimen of patients with histiocytic neoplasm. The Tempus xO Assay (Tempus Labs; Chicago, IL) combines a 1,711 gene targeted somatic and germline DNA sequencing panel with RNA-sequencing to detect both germline and somatic single nucleotide polymorphisms, indels, copy number variants, and gene rearrangements causing chimeric mRNA transcript expression in a wide array of solid tumor types. The assay utilizes formalin-fixed paraffin-embedded tumor samples and matched blood samples. TMB was calculated and reported as somatic mutations in tumor tissue per million base-pairs or mut/Mb. RNA sequencing was utilized to assess for PD-L1 and PD-1 gene expressions as compared to matched tumor and normal reference sets. Both PD-L1 and PD-1 gene expressions were reported as percentiles. DNA mismatch repair status was predicted by analysis of alterations in five common mismatch repair genes in somatic and germline DNA (MSH2, MSH6, MLH1, PMS2, and EPCAM). If there were no alterations identified in these genes, the mismatch repair status was predicted as microsatellite stable (MSS). Results A total of 13 patients with histiocytic neoplasms were included in the study. The distribution of individual histiocytic neoplasms was as follows: RDD (n=9), ECD (n=3), and LCH (n=1). The median TMB for RDD and ECD patients was 0.17 mut/Mb. For the one patient with LCH, the TMB level was 0.51 mut/Mb. Individual TMB levels are shown in figure 1. PD-L1 and PD-1 expression levels are depicted in table 1. Compared to normal reference sets, the PD-L1 expression was elevated in one patient each with RDD and ECD, and PD-1 expression was elevated in two patients each with RDD and ECD. For both ECD patients with higher PD-1 expression, NGS also showed presence of BRAF-V600E in the tumor tissue. The LCH patient had a low level of PD-L1 and PD-1 expression. For patients where evaluation of DNA mismatch repair was feasible on the tissue specimen (n=4), none showed related somatic or germline alterations. Conclusions In our series, the histiocytic neoplasms RDD, ECD, and LCH demonstrated low levels of TMB. None of the RDD and ECD patients were found to have alterations in DNA mismatch repair genes. Other markers of immunotherapy such as PD-L1/PD-1 expression appeared to be higher in ECD patients with BRAF-V600E, but in only a small subset of RDD patients. The low TMB seen in our study suggests that these histiocytic neoplasms may be less likely to respond to immune checkpoint inhibitors such as anti-PD-1 and anti-PD-L1 agents as compared to the tumors with high TMB. Disclosures No relevant conflicts of interest to declare.

Abstract Background: Early integration of Palliative Care (PC) have shown to improve survival in some solid malignancies such as lung and colon cancers. In this study we sought to analyze the PC utilization in acute myeloid leukemia (AML) patients. Methods: Using the National Cancer Data Base (NCDB) Participant User File, we extracted patient-level data of patients with AML reported between 2004 to 2015.Patients who received pain management and/or other palliative procedures were considered as PC utilizers. After excluding the cases with acute promyelocytic leukemia t (15, 17) (given its excellent prognosis), we classified the AML into three groups- AML with genetic abnormalities, therapy related AML and AML with dysplasia. Other co-variates included in the analysis were age, sex, race, origin, Charlson-Deyo comorbidity score, insurance status, household income, educational status, facility type (academic vs non-academic) and year of diagnosis. Multivariate logistic regression was performed to identify the predictors of palliative care utilization. Statistical analysis was done using PC SPSS v24.0. Results: Of 102,778 patients, 3.4% (n=3504) received PC as initial treatment. PC utilization increased significantly from 2004-2006 to 2013-2015 (2.5% vs 3.9%, p < 0.001). Individuals of non-Hispanic origin (as compared to that of Hispanics) are more likely to receive PC as compared to that of non-Hispanics. (3.5 vs 1.8%, p<0.001). The patterns of PC utilization at non-academic centers were much higher than that of academic centers (4.4% vs 2.9%, p<0.001). As compared to that of AML, not otherwise specified subtype (3.3%), therapy-related AML (4%) and AML with dysplasia (4.3%) had higher rates of PC utilization, whereas individuals with AML with genetic abnormalities have lesser rates of PC utilization (1.9%) (p<0.001, all comparisons). Significant predictors of PC on multivariable regression are listed in the Table and forest plot. Conclusions: We noticed a differential utilization of palliative care based on the histological subtype of AML. The lesser utilization of PC in AML with certain genetic abnormalities may be attributed to their better overall survival outcomes. Though we noticed an increased trend in PC utilization over the past decade, the overall PC utilization in AML is markedly low and plagued by origin and socio-economic status. Disclosures No relevant conflicts of interest to declare.