Young, Jason R.

7018 Background: Langerhans cell histiocytosis (LCH) is a rare histiocytic neoplasm driven by MAPK-ERK mutations in majority of patients. Contemporary data on treatments and outcomes in adult LCH are lacking. Hence, we undertook this study to analyze a large cohort of adult LCH patients. Methods: This was a retrospective study of adult (≥18 years) LCH patients seen at our institution between 1998 and 2018. Results: We included 186 patients with adult LCH (median age 43; 19-88), and 54% were females. 70% of patients were diagnosed after 2007. Common presenting symptoms were cough/dyspnea (30%), rash (17%), pain/swelling in head (17%), and diabetes insipidus (10%). 70 (38%) patients had multisystem LCH, 62 (33%) had isolated pulmonary LCH, and 35 (19%) had unifocal LCH. Common sites of involvement included lung (59%), bone (37%), skin (21%), and nervous system (16%). 121 (65%) were smokers; 48% of these had lung disease, while 52% had multisystem disease. 18 of 31 tested (58%) patients had BRAF-V600E mutation. Most common first-line treatment was smoking cessation in 24 patients, and led to an overall response rate (ORR) of 83% in pulmonary lesions. Radiation therapy was used in 11 patients, and led to an ORR 82%. Surgical resection of lesion was done in 23 patients, with relapses in 24%. Systemic therapies were used in 78 (42%) patients (Table). Most common first-line systemic therapy was cladribine with ORR of 78%. Vemurafenib was used in 3 patients with BRAF-V600E, leading to an ORR of 67% . After a median follow-up of 23 months (0-261), 21 patients had died. Of these, 10 died of progressive LCH. Median OS was not reached, and mean OS was 196 months. Conclusions: This is the largest contemporary series of adult LCH. It shows that diverse clinical spectrum, ranging from benign course to a progressive multisystem disease. Although smoking cessation was an effective treatment for pulmonary LCH, a large subset required systemic chemotherapy. [Table: see text]

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.

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.

Abstract Introduction Primary testicular lymphoma (PTL) and testicular involvement of systemic lymphoma (secondary testicular lymphoma, STL) are uncommon. Most testicular lymphomas are aggressive B-cell lymphomas and portend a high risk of extranodal relapse, including CNS relapse. As such, when testicular lymphoma is identified, the management strategy is often changed to include CNS prophylaxis. It is, therefore, essential to evaluate testicular involvement in diagnosis and staging. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is a standard imaging modality to stage aggressive lymphoma. Physiologic testicular FDG activity can be challenging to distinguish from involvement by lymphoma given a wide range of normal. An imaging threshold for testicular PET uptake would be clinically relevant and would help guide management. We compare testicular FDG avidity in testicular lymphoma with physiologic testicular FDG avidity. Methods Records of patients (pts) diagnosed with PTL or STL from 2002-2018 enrolled in the University of Iowa/Mayo Clinic Lymphoma SPORE Molecular Epidemiology Resource were reviewed, yielding 36 pts with testicular lymphoma. Physiologic testicular avidity by FDG PET/CT was determined from analysis of 70 randomly selected patients who received FDG PET/CT from 2013-2018 prior to treatment for non-lymphoma indications including pulmonary nodule, lung carcinoma, head & neck squamous cell carcinoma, gastrointestinal carcinomas, and metastatic melanoma, without known hematologic malignancy, testicular pathology, or history of testicular infection/surgery by medical chart review. Imaging parameters compared in this analysis were SUVmax and SUVmean. All FDG PET/CT exams were reviewed centrally by a nuclear medicine radiologist and a radiology resident. Results Of the 36 pts with testicular lymphoma, 19 had an orchiectomy prior to FDG PET/CT and 7 pts did not have a staging FDG PET/CT scan. Of the 10 pts with intact testes at the time of staging FDG PET/CT, 1 pt with low-grade lymphoma was excluded. 9 pts with aggressive lymphomas were included in this analysis: 7 pts with diffuse large B cell lymphoma (DLBCL), and 1 pt each with Burkitt lymphoma and peripheral T-cell lymphoma, not otherwise specified. Testicular lymphoma was diagnosed by orchiectomy in 3 pts, and by percutaneous biopsy in 3 pts. 3 pts did not have tissue sampling of testes or scrotal contents, but had an overtly FDG-avid testicle highly suggestive of lymphomatous involvement. These 3 pts had biopsy-proven lymphoma in parotid, bone marrow, and stomach, respectively, with mean testicular SUVmax 6.8 among the 3 pts. The median age in this analysis cohort was 62 years (range 35-88). Of the 7 analyzed DLBCL pts, 6 were non-germinal center B-cell, and 1 was germinal center B-cell. The 70 control pts had a median age of 55 years (range 18-90). In known testicular lymphoma cases and control pts, SUVmax and SUVmean were assessed from the most FDG-avid testicle. Median SUVmax for the testicular lymphoma cases was 13.3 (range 5.5-29.9), compared to a median of 3.8 (range 2.1-5.5) for controls (Wilcoxon p <0.0001). Median SUVmean for testicular lymphoma was 9.2 (range 3.3-18.6), compared to a median of 3.1 (range 1.8-4.8) for controls (Wilcoxon p <0.0001) (Figure). Based on this dataset, an SUVmax cutoff of 5.0 has a sensitivity of 100% (95% CI 66.3-100) and a specificity of 98.6% (98% CI 92.3-99.9) for the detection of testicular involvement by an aggressive lymphoma. Conclusions FDG PET/CT shows significantly greater FDG avidity for testicular aggressive lymphomas as compared with physiologic testicular FDG uptake in this single institution study with centralized radiology review of cases and controls. Testicular FDG avidity greater than an SUVmax 5.0 in staging aggressive lymphoma is highly suggestive for testicular involvement, warranting follow-up clinical exam and ultrasound, at a minimum. In addition, testicles with SUVmax <5.0 in a patient with known lymphoma but no symptoms or signs of testicular involvement should be considered negative for the purposes of staging and treatment planning. A pragmatic limitation of this study is that most patients with testicular involvement of lymphoma underwent orchiectomy prior to FDG PET/CT scan, which decreased our sample size. Larger, pooled studies would be helpful to validate these clinically relevant findings. Figure. Figure. Disclosures Witzig: Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Cerhan:Celgene: Research Funding; Jannsen: Other: Scientific Advisory Board; Nanostring: Research Funding.

Abstract Introduction: Outcomes of multidisciplinary and molecular tumor boards have been reported. Lymphoma specific tumor board outcomes have not been reported in the molecular era. In addition, the utility of multi-site, interactive tumor boards using videoconference technology are not widely reported. We prospectively followed the outcomes of a multidisciplinary multi-site lymphoma tumor board in the molecular era and during a change in the revision of the World Health Organization Classification in first published in 2016. Methods: The Mayo Clinic Lymphoma Tumor Board is a component of the international Mayo Clinic Care Network (MCCN). The format includes the clinical case presentation, presentation of radiology and hematopathology findings by the appropriate specialist, proposed treatment options, review of the literature pertinent to the case, and discussion followed by recommendations. Requirement for presentation includes having a diagnosis of lymphoma with pathology reviewed at Mayo Clinic, Rochester, MN (MCR). Pathology and radiology material, when relevant to the case, are required to be reviewed at MCR and presented by MCR pathologists/radiologists. Patients must be presented prospectively, and have active clinical issues or questions to be addressed. Four cases are presented per 60-minute meeting. 309 consecutive highly selected cases with a diagnosis of lymphoma were presented at the Mayo Clinic Lymphoma Tumor Board from 2014 to 2018. The pathology material was independently reviewed by the presenting hematopathologists and radiology material by the presenting radiologist. Participants are office based and included multiple members of the health care team which also incudes pharmacists, clinical research associates affiliated with lymphoma research, and physicians in training. Recommendations were prospectively tracked for changes in radiology interpretation, pathologic diagnosis, and treatment approaches. Actual follow-up of all patients after the meeting was not allowed in the MCCN. Participation in the meeting can be either via in-room attendance at MCR, video conference at a participating MCCN site, or via non-participatory live-stream online. Results: 309 cases were presented were presented from 2014-2018. 258 cases were from MCR, and 51 were not physically seen at MCR. 16 cases were presented at a subsequent meeting for further recommendations in the course of their disease after the initial presentation. 54% of patients presented had changes in some aspect of their care as a result of the meeting. Changes in radiologic interpretation occurred in 5 (1.6%) patients. The pathologic diagnosis changed in 27 (8.7%). Additional testing was recommended in 44 (14%). Clinical management changes were recommended in 90 (29%) cases. These included alterations in treatment approach in 43 (14%), change from undecided to pursuit of treatment 10 (3%), change from undecided regarding treatment approach to further diagnostic testing 4 (1.3%), change from observation to treatment 9 (3%), change from treatment to observation 4 (1.3%), and treatment to further tests in 2 (0.6%) Site in room average attendance (internal/external) was 16.8/8.6. Non-participatory live-stream attendance was not possible to track. In an annual electronic evaluation of this activity, 93% of the responders reported an improvement in knowledge and competence, and 100% recommended no changes to the format of the conference. Enhancements over time have included Continuous Medical Education credit, an in room microscope, and real-time radiology images. Selected cases will now be on line on an international web site. Conclusion: In this highly selected group of lymphoma cases from multiple sites over a 4-year period, 54% of the (167/309) case presentations resulted in changes to some aspect of care as a direct result of this tumor board. A multidisciplinary lymphoma tumor board approach was of value, efficacious, and meaningfully impacted lymphoma patients while substantially enhancing interdisciplinary interactions. Disclosures Ansell: Celldex: Research Funding; Seattle Genetics: Research Funding; Takeda: Research Funding; Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Merck & Co: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; Trillium: Research Funding; Affimed: Research Funding.