Ali, Haadi

Abstract Introduction: Targeted therapy yields deep and durable response in histiocytic neoplasms.However, relapse rate following interruption is high at 75-77%, with a median time to relapse 6-9 months in previous studies. Outcomes after discontinuation in those who have already achieved a durable response are not well understood and are the focus of this study. Methods: We performed a multicenter retrospective study, including 4 US centers, including patients with histiocytic disorders treated with BRAF inhibitor (BRAFi), MEK inhibitor (MEKi), or combination BRAF/MEKi, and whose therapy was interrupted after ≥12 months of therapy following a best response of partial (PR) or complete response (CR). Progression-free survival (PFS) and overall survival (OS) were analyzed with Kaplan-Meier method. Cox regression was performed to identify clinical and molecular factors that are associated with PFS. Results: 26 patients were included (median age 55 [range 12-72]; male 53.8%; Caucasian 69.2%). Most predominant histology was Erdheim-Chester Disease (ECD) (n=15, 57.5%), followed by mixed histiocytosis (n=5, 19.2%). Rosai-Dorfman Disease (RDD) (n=4, 15.4%), and Langerhans Cell Histiocytosis (LCH) (n=2, 7.7%). All had BRAF V600E analysis and 10 (38.5%) were positive. 19 patients underwent additional molecular testing; alternative mutations identified included MAP2K1/2 (n=6, 23.1%), NRAS (n=1, 3.8%), RAF1 (n=1, 3.8%), ASXL1 (n=1, 3.8%), and SRSF2 (n=1, 3.8%). Targeted therapy was given as frontline therapy (n=8, 30.8%) or in the relapsed refractory setting (n=18, 69.2%) with median 1 prior line of therapy (range 0-7). Targeted therapies include BRAFi (n=5, 19.2%; 2 dabrafenib, 3 vemurafenib), MEKi (n=17, 65.4%; 14 cobimetinib, 3 trametinib), and BRAF/MEKi (n=4, 15.4%; 3 dabrafenib/trametinib, 1 vemurafenib/cobimetinib). PR and CR occurred in 8 (30.8%) and 18 (69.2%) patients, respectively. The median duration of treatment was 32 months (range 13-60) (12-24 months: 9 [34.6%]; 24-36 months: 7 [26.9%]; >36 months: 10 [38.5%]). Median time from initiation of targeted therapy to best response was 6 months (<6 months: 14 [53.8%]; 6-12 months: 5 [19.2%]; >12 months: 7 [26.9%]). Median duration from best response to drug discontinuation was 19 months (12-24 months: 14 [53.8%]; 24-36 months: 7 [26.9%]; >36 months: 5[19.2%]). Reasons for drug discontinuation include toxicity (n=8, 30.8%), patient preference (n=13, 50.0%), cost prohibition (n=1, 3.8%), and other critical medical conditions (n= 4,15.4%). Eleven patients (42.3%) experienced disease progression after discontinuation of targeted therapy, 5 patients progressed within 6 months. Systemic and CNS progression were captured by PET/CT and MRI brain, respectively. At median follow-up of 33.0 months (95%CI 24.3-47.1), median PFS, defined by time from targeted therapy discontinuation to progression or death, was 29 months (95% confidence interval [CI] not estimable). Median OS was not reached. In Cox regression model, BRAF V600E mutation (hazard ratio [HR] 4.16, 95% CI 1.10-15.70, p 0.036) and CNS involvement (HR 4.64, 95% CI 1.21-17.67, p 0.025) were associated with inferior PFS. MEKi containing regimen trended toward improved PFS (HR 0.35, 95%CI 0.10-1.21, p 0.097). There was no difference in PFS when assessing demographics, histology, prior therapies, best response to targeted therapy, treatment duration, or time from best response to discontinuation. Of the 11 patients with progression, 9 were re-challenged with targeted therapy (7 switched class), 2 did not receive next line therapy (1 transitioned to hospice and passed from progression, 1 has pending evaluation for next line therapy). Of 6 with response assessments, all recaptured response (1 CR, 5 PR), and none had progressed by data cutoff. Conclusions: In patients with histiocytic neoplasm and prior durable response to targeted therapy, ~40% experienced disease progression after treatment discontinuation. BRAF V600E mutation and CNS disease are associated with inferior PFS, suggesting these subgroups may not be appropriate for limited duration of treatment. Novel approaches are needed in these high-risk patients.

Abstract Introduction: Langerhans Cell Histiocytosis (LCH) is a rare histiocytic neoplasm, with approximately 90% of patients exhibiting alterations in the MAPK pathway. BRAF and MEK inhibitors have shown promising results in treating MAPK pathway-altered LCH. However, treatment interruptions due to adverse effects are common, and limited access to targeted therapies complicates care globally. While chemotherapy remains a common treatment for LCH, the outcomes for patients with MAPK pathway-altered LCH specifically receiving chemotherapy are still unclear. Methods: This multi-institutional international retrospective cohort study analyzed adult patients with BRAF or MAP2K (gain-of-function, GOF) altered LCH that were consecutively seen at Mayo Clinic, MN, AZ, and FL, University of Alabama at Birmingham, and Peking Union Medical College Hospital in China between 2007 and 2024. All patients who were included in this study were treated with chemotherapy, and those who have received targeted therapies or other modalities of frontline treatment were excluded. All time-to-event analyses were performed from the frontline therapy initiation, using the Kaplan-Meier method. Progression-free survival (PFS) included death and progression as events and was measured from the time of treatment initiation. The response assessment was based on radiographic evaluation in accordance with the most recent Histiocyte Society consensus guideline. Risk organ involvement was defined as disease involving the liver, spleen, bone marrow or central nervous system. Results: A total of 63 patients with LCH were included. The median age of the population was 34 years (range: 27-43), and males were 59%. Risk organ involvement was seen in 44 (70%) of patients and multisystemic LCH was observed in 48 (76%) patients. Among the 63 patients, BRAF gain-of-function alterations were observed in 79%, MAP2K mutations in 19%, and BRAF fusions in 2%. Of the BRAF gain-of-function alterations, BRAFV600E mutation was seen in 64% patients and [p.N486_P490del] deletion in 36%. There was no significant difference in organ involvement (single-system versus multisystem) or risk organ involvement between patients with BRAF and MAP2K alterations. All 63 patients received systemic therapy with chemotherapy and the regimens included Cytarabine (n=43), Cladribine (n=5), Etoposide (n=1), Methotrexate (n=1), and combined Methotrexate and Cytarabine (n=13). The median follow-up for the entire cohort was 3.8 years (range 3.2–5.0 years), with similar durations observed in patients with single-system vs. multisystem involvement and those with risk-organ involvement vs. no risk-organ involvement. The overall response rate among patients who received chemotherapy was 89%, with complete responses in 15 patients (26%) and partial responses in 40 patients (64.5%). The median progression-free survival (PFS) for the entire cohort was 2.61 years (95% CI: 2.06–NA). The 3-year PFS did not significantly differ based on risk organ involvement: 50.6% (95% CI: 36–71) for patients with risk organ involvement versus 47.4% (95% CI: 28–81) for those without, p=0.52. Patients with single-system disease experienced longer PFS compared to those with multisystem disease; the 3-year PFS was 80.2% (95% CI: 58.7–100) versus 42.2% (95% CI: 29–61.5), respectively, p=0.04. Conclusions: Our results indicate that LCH patients with a GOF alteration in the MAPK pathway derive significant clinical benefit from chemotherapy, achieving deep and durable responses. Therefore, patients should not be excluded from treatment due to the absence of targeted therapies, as they can still attain substantial responses and clinical improvement with chemotherapy, even in the context of MAPK pathway-driven disease.

Introduction: Autoimmunity in Rosai-Dorfman disease (RDD) has been reported in several case reports and small case series. The recent consensus RDD guidelines even classify “immune-related RDD” as a distinct entity, but little is known about the prevalence and patterns of autoimmune conditions in this rare disease. We conducted this study to evaluate a large cohort of patients with RDD for concomitant autoimmunity. Methods: We conducted a retrospective review of cases diagnosed with RDD from five referral centers globally. Data pertaining to autoimmunity were captured in terms of serology and a clinical diagnosis of autoimmune disease (AID) and compared to previously reported prevalence of AID and autoimmunity in the general population and in patients with other lymphomas. Results: We included 157 patients diagnosed with RDD from 2003-2023. Median age at the time of RDD diagnosis was 48 years, IQR 35.5-60. This included 103 females (65.6%) and 54 male (34.4%). Racial distribution included 54 Black (34.4%), 52 White (33.1%), 40 Asian (25.5%), 7 Middle Eastern (4.5%) and 4 other (2.5%). 83 patients had multi-systemic disease (52.8%) and 74 had single organ involvement (47.2%). Most common organs involved were skin/subcutaneous tissue (78, 49.7%), lymph nodes (63, 40.1%), bone (54, 34.2%). Tissue next generation sequencing data was available for 100 patients (63.7 %) and showed KRAS mutation (19, 19 %), MAP2K/MEK (13, 13%), other mutations (27, 27 %), and no mutations (41, 41%). Mean ESR at diagnosis of RDD was 28.42 mm/Hr and mean CRP was 19.5 mg/L. In our cohort, 28 patients (17.8%) were diagnosed with an AID. 19 (67.8%) were diagnosed with the AID prior to the diagnosis of RDD. Most common AID was systemic lupus erythematosus (6, 21.4%), rheumatoid arthritis (5, 17.8%), autoimmune hemolytic anemia (3, 10.7%), polymyalgia rheumatica (2, 7.1%). AID was more common in female vs male (64.3% vs 35.7%, p 0.8) and were more commonly seen in patients with multisystem compared to single organ RDD (60.7% vs 39.3%, p 0.3). Mean ESR and CRP at the time of RDD diagnosis in patients with AID were 40.63 mm/Hr and 37.04 mg/L respectively. Autoimmune antibodies were tested in 90 patients (57.3%), of which 43 (47.8%) were positive for atleast one autoantibody which included 15 patients (16.7%) with AID and a positive autoantibody and 6 (6.6%) with AID and negative antibodies (p 0.01). Most common antibodies were ANA (29/83, 34.9%), 42.3% with a titer higher than 1:160. Other antibodies include RF (10/60, 16.67%), anti-neutrophilic cytoplasmic antibody (3/19, 15.8%), double stranded DNA (6/56, 10.7%). Positive Antibodies were more common in female compared to male patients (72% vs 23%, p 0.04) and in patients from China compared to North America (45.7% vs 22.6%, p 0.007). Autoantibody positivity was common in multi-system vs single organ RDD (53.5% vs 46.5%, p 0.9). Mean ESR and CRP in this group of patients were 34.54 mm/Hr and 23.93 mg/L respectively. Median duration of follow up for our cohort was 32 months (IQR 14-65). Five-year survival was 93.4%. There were a total 8 deaths reported in the cohort, none of which were in patients with underlying AID. In a multivariable analysis, AID was associated with race (odds ratio [OR] for Middle Eastern compared with Chinese, OR 7, p=0.02) but other factors like organ involvement, mutational status, sex and age at diagnosis were not significant. Conclusions: Our study reveals a high prevalence of autoimmunity in RDD, both in terms of AID (17.8 %) and positive autoantibodies (47.8 %), which is much higher than the general population rates of approximately 3% and 16% respectively, and higher than patients with non-Hodgkin lymphoma, 7.6% and 39%, respectively. There was a trend toward association of AID with multisystem RDD and among individuals from North America and Middle East compared to China, although auto-antibody positivity was more common in Chinese patients. Mean ESR and CRP at the time of diagnosis of RDD was higher in the patients who had AID. We did not find any statistically significant association between AID and autoantibody positivity with the underlying driver mutation. Nearly half of the patients with RDD who also had AID did not have a positive autoantibody, thereby implying the need of clinical evaluation for rheumatological symptoms rather than empiric serological testing. Overall, this study also highlights the need to explore the biological link between RDD and autoimmunity.