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Importance Tau positron emission tomography (PET) allows in vivo detection of neurofibrillary tangles, a core neuropathologic feature of Alzheimer disease (AD). Objective To provide estimates of the frequency of tau PET positivity and its associated risk of clinical outcomes. Design, Setting, and Participants Longitudinal study using data pooled from 21 cohorts, comprising a convenience sample of 6514 participants from 13 countries, collected between January 2013 and June 2024. Cognitively unimpaired individuals and patients with a clinical diagnosis of mild cognitive impairment (MCI), AD dementia, or other neurodegenerative disorders were included. Exposures Tau PET with flortaucipir F 18, amyloid-β (Aβ) PET, and clinical examinations. Tau PET scans were visually rated as positive according to a US Food and Drug Administration– and European Medicines Agency–approved method, designed to indicate the presence of advanced neurofibrillary tangle pathology (Braak stages V-VI). Main Outcomes and Measures Frequency of tau PET positivity and absolute risk of clinical progression (eg, progression to MCI or dementia). Results Among the 6514 participants (mean age, 69.5 years; 50.5% female), median follow-up time ranged from 1.5 to 4.0 years. Of 3487 cognitively unimpaired participants, 349 (9.8%) were tau PET positive; the estimated frequency of tau PET positivity was less than 1% in those aged younger than 50 years, and increased from 3% (95% CI, 2%-4%) at 60 years to 19% (95% CI, 16%-24%) at 90 years. Tau PET positivity frequency estimates increased across MCI and AD dementia clinical diagnoses (43% [95% CI, 41%-46%] and 79% [95% CI, 77%-82%] at 75 years, respectively). Most tau PET–positive individuals (92%) were also Aβ PET positive. Cognitively unimpaired participants who were positive for both Aβ PET and tau PET had a higher absolute risk of progression to MCI or dementia over the following 5 years (57% [95% CI, 45%-71%]) compared with both Aβ PET–positive/tau PET–negative (17% [95% CI, 13%-22%]) and Aβ PET–negative/tau PET–negative (6% [95% CI, 5%-8%]) individuals. Among participants with MCI at the time of the tau PET scan, an Aβ PET–positive/tau PET–positive profile was associated with a 5-year absolute risk of progression to dementia of 70% (95% CI, 59%-81%). Conclusions and Relevance In a large convenience sample, a positive tau PET scan occurred at a nonnegligible rate among cognitively unimpaired individuals, and the combination of Aβ PET positivity and tau PET positivity was associated with a high risk of clinical progression in both preclinical and symptomatic stages of AD. These findings underscore the potential of tau PET as a biomarker for staging AD pathology.

ABSTRACTMonoclonal gammopathy of undetermined significance (MGUS) is the term used for a minimal clonal expansion of plasma cells that is most typically detected by the presence of a small serum monoclonal protein. For most—but not all—patients, the presence of a small monoclonal protein will have no clinical significance at the time of recognition or even over time. It is imperative, therefore, that a careful—but sensible—evaluation be performed both at the time of recognition and subsequently because these monoclonal may represent significant pathology including diseases such as multiple myeloma, low grade lymphoma or any of the diseases captured under the moniker of monoclonal gammopathy of clinical significance (MGCS), which includes—but is not limited to—immunoglobulin light chain amyloidosis and POEMS syndrome. Herein is a discussion of the diagnosis and follow‐up MGUS and MGCS.

ABSTRACTCastleman disease is a term that represents a spectrum of diseases whose driving factors are poorly understood. Increased interest prompted by the Castleman's Disease Collaborative Network has led to a better understanding of classification, which will lead to a better understanding of underlying pathology and best practices. It is essential that this entity be recognized and correctly classified by anatomic classification (unicentric, oligocentric, and multicentric), by histopathology (the gradient of hypervascular to plasmacytic), and by clinical phenotype (NOS, TAFRO, IPL, HHV8‐associated, or POEMS‐associated). Most of what we know about therapy is from retrospective studies rather than prospective therapeutic trials, but data are emerging through collaboration. The mainstay of therapy for unicentric disease is surgery. For multicentric disease interleukin‐6 blockade is essential for the non‐POEMS, non‐HHV8 multicentric cases, rituximab‐based (plus or minus antiviral) therapy for HHV8 associated cases, and IL‐6 blockade versus plasma cell directed therapy for the POEMS subtype.

Disease response and progression assessment in multiple myeloma (MM) is based on various measurements of monoclonal protein (serum and urine protein electrophoresis, serum free light chain (FLC, and or quantitative immunoglobulins). Currently, the IMWG consensus response criteria require two sequential assessments of any one marker made at any time before confirmation of disease progression and the institution of any new therapy. However, this can be cumbersome in clinical trials. Herein, we hypothesized that if two markers meet the progression criteria simultaneously, a repeat of either will not be necessary for confirmation. We retrospectively studied all sequential patients with myeloma enrolled in clinical trials at Mayo Clinic. We identified 583 episodes of confirmed progression in our study. Among the 583 progression episodes, nearly 70% (sensitivity of the simultaneous criteria) met the two simultaneous variable criteria at the first testing, indicating progression. Conversely, among 413 patients who met progression criteria by two simultaneous values, 98% (specificity of the simultaneous criteria) of patients subsequently had confirmed progression by sequential values. In summary, for patients with two disease burden markers meeting the simultaneous progression criteria, sequential assessment either one for confirmation may not be necessary to determine disease progression.

Abstract Background High-grade gliomas (HGG) have a poor prognosis despite aggressive treatment. Severe, persistent lymphopenia occurring in HGG patients after concurrent chemoradiation is associated with worse survival. NT-I7, a long-acting interleukin-7 analog, has been shown to increase CD4 and CD8 counts in healthy, septic, and HIV-positive adults. This multi-institutional, NCI-funded dose-escalation trial is the first to evaluate NT-I7 safety and activity in HGG patients with severe treatment-related lymphopenia (TRL) and the effect of co-administered glucocorticoids. Methods Eligible HGG patients had CD4 counts <300 cells/mm3 after 5 weeks of standard chemoradiation and were receiving either ≤0.75 or ≥4 mg/day of dexamethasone. Patients received a single intramuscular dose of NT-I7 (60 or 360 µg/kg) post-chemoradiation, followed by safety evaluation and multi-parameter, longitudinal monitoring of lymphocyte populations and immunologic function. Results NT-I7 was well tolerated in all 12 patients (median age 64; median CD4 count 161 cells/mm³) before the study closed prematurely. Absolute lymphocyte counts doubled in 83% (10/12; 95% CI: 51.6%-97.9%) of patients, and CD4 counts doubled in 42% (5/12; 95% CI: 15.2%-72.3%) of patients. Glucocorticoid use did not significantly affect CD4 or lymphocyte increases. Correlative immune profiling revealed increased Ki67 expression in CD4 (P < .005) and CD8 (P < .05) after one week, along with the expansion of CD4 and CD8 T-cell subsets and CD56 + natural killer cells. Conclusions NT-I7 is well tolerated and effectively increases lymphocyte and CD4 counts in severe TRL patients, regardless of glucocorticoid use, suggesting its potential to mitigate TRL and improve outcomes in HGG.

Abstract How do brain networks limit seizure activity? In the interictal suppression hypothesis, we recently postulated that high inward connectivity to seizure onset zones (SOZs) from non-involved zones (NIZs) is a sign of broader network suppression. If broad networks appear to be responsible for interictal SOZ suppression, what changes during seizure initiation, spread and termination? For patients with drug-resistant epilepsy, intracranial monitoring offers a view into the electrographic networks that organize around and in response to the SOZ. In this manuscript, we investigate network dynamics in the peri-ictal periods to assess possible mechanisms of seizure suppression and the consequences of this suppression being overwhelmed. Peri-ictal network dynamics were derived from stereo electroencephalography recordings from 75 patients with drug-resistant epilepsy undergoing presurgical evaluation at Vanderbilt University Medical Center. We computed directed connectivity from 5 s windows in the periods between, immediately before, during and after 668 seizures. We aligned connectivity matrices across seizures and patients, then calculated net connectivity changes from the SOZ, propagative zone and NIZ. Across all seizure types, we observed two phases: a rapid increase in directed communication towards the SOZ, followed by a collapse in network connectivity. During the first phase, SOZs could be distinguished from all other regions (one-way ANOVA, P = 8.32 × 10−19–2.22 × 10−7). In the second phase and post-ictal period, SOZ inward connectivity decreased yet remained distinct (one-way ANOVA, P = 2.58 × 10−10–1.66 × 10−2). NIZs appeared to drive increased SOZ connectivity while intra-NIZ connectivity decreased concordantly. Stratifying by seizure subtype, we found that consciousness-impairing seizures decrease inward connectivity from the NIZ earlier than consciousness-sparing seizures (one-way ANOVA, P < 0.01 after false discovery correction). Tracking network reorganization against a surrogate for seizure involvement highlighted a possible antagonism between seizure propagation and the ability of the NIZ to maintain high connectivity to the SOZ. Finally, we found that inclusion of peri-ictal connectivity improved the accuracy of SOZ classification from previous models to a combined area under the curve of 93%. Overall, NIZs appear actively to increase inhibitory signaling towards the SOZ during seizure onset, possibly to thwart seizure activity. Although inhibition appears insufficient to prevent seizure onset, the inability to restrict seizure propagation might contribute to loss of consciousness during larger seizures. Dynamic connectivity patterns uncovered in this work might: (i) facilitate accurate delineation of surgical targets in focal epilepsy; (ii) reveal why interictal suppression of SOZs might be insufficient to prevent all seizures; and (iii) provide insight into mechanisms of loss of consciousness during certain seizures.

10019 Background: The reported incidence of second malignant neoplasms (SMN) in long-term survivors of Hodgkin lymphoma (HL) is derived from patients treated with outdated radiation therapy (RT) techniques. We modeled the risk of SMN in pediatric patients with high-risk classic HL treated with modern mediastinal RT. Methods: In patients who received mediastinal RT on the Children’s Oncology Group study AHOD1331, we modeled the lifetime attributable risk (LAR) at 70 years of age of thyroid, lung, and breast carcinoma. This value indicates the absolute increased risk of SMN at 70 years of age due to RT, above the baseline population risk (mean baseline rates at 70 years of age are 0.7%, 3.3%, and 8.9% for thyroid, lung, and breast carcinoma, respectively, https://seer.cancer.gov/data/ ). Results: In 296 patients who received protocol-directed mediastinal RT, median age at diagnosis was 15.1 years, 55% were female, and 98% had large mediastinal adenopathy. Following 5 cycles of chemotherapy, patients received RT targeting the mediastinum based on criteria of this study; in addition, some patients received RT to other supradiaphragmatic sites that contained slowly responding lesions, including the axilla (n = 3, 1%), lung (n = 7, 2.4%), upper neck (n = 4, 1.3%), and lower neck (n = 8, 2.7%). The RT modality was proton therapy in 25.3%, photon intensity modulated RT (IMRT) in 45.6%, and photon 3-dimensional conformal RT (3D-CRT) in 27.7%. The RT prescription dose was 21 Gy in 83% and 30 Gy in 16% who had a partial metabolic response at the completion of chemotherapy. The mean (range) doses to the thyroid, lungs, and breasts were 12.8 Gy (0-30.3), 8.0 Gy (0.1-15.2), and 4.2 Gy (0.2-14.5), respectively. For the complete cohort, the mean LAR at 70 years of age of thyroid carcinoma was 0.063% and of lung carcinoma was 5.34%. For females, the mean LAR at 70 years of age of breast carcinoma was 2.92%. The Table summarizes the LAR for each SMN, stratified by RT modality. Conclusions: In patients treated with mediastinal RT on a recent multi-institutional study of pediatric HL, the predicted long-term risk of SMN is substantially lower than in historical cohorts. Clinicians should consider the toxicity associated with a current RT approach when selecting therapies and counseling patients. Clinical trial information: NCT02166463 , this is a post hoc modeling study that includes patients enrolled on this study. Mean [range] lifetime attributable risk (%) at an attained age of 70 years for thyroid, lung, and breast carcinoma. Thyroid Lung Breast (females) 3D-CRT 0.046 [0.002-0.332]N=81 5.07 [0.12-10.82]N=82 1.82 [0.67-5.98]N=46 IMRT 0.064 [0.001-0.386]N=135 6.24 [2.22-11.79]N=135 4.36 [0.66-8.43]N=76 Proton 0.086 [0-1.160]N=74 4.15 [0.94-7.77]N=75 1.45 [0.17-7.23]N=40

11549 Background: Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm with a subset associated with unicentric Castleman disease (UCD). However, the impact of CD association on clinicopathologic features and survival outcomes remains unclear. This study aims to elucidate differences in disease characteristics and outcomes in FDCS with and without CD to guide future research and clinical practice. Methods: We retrospectively analyzed 41 FDCS patients seen at Mayo Clinic between January 2000 and December 2024. Patients were categorized into CD-related (n = 9) and FDCS-only (n = 32) groups. Demographic, clinical, pathological, and survival data were compared. Kaplan-Meier survival analyses were used to evaluate overall survival (OS) and progression-free survival (PFS). Epstein-Barr virus-associated inflammatory FDCS were excluded. Results: The CD-related group was younger at diagnosis (46.0 vs. 58.0 years, p = 0.041). Among those with CD-related FDCS, FDCS was diagnosed concurrently as CD in 6/9 (66.7%) and after the diagnosis of CD in 3/9 (33.3%). The FDCS-only patients were more likely to have extranodal disease (71.9% vs. 22.2%) and to have metastasis (62.5% vs 22.2%). One CD-related FDCS patient had paraneoplastic pemphigus. Among 11 patients with next-generation sequencing (NGS) results, 9 had pathogenic mutations. The most common pathogenic mutations included CDKN2A, CDKN2B, and TRAF3 copy number losses. Surgery was the preferred first-line intervention in FDCS-only and CD-related FDCS groups (19/32, 59.4% vs. 6/9, 66.7%). Eight out of 32 (25.0%) of the FDCS-only group received chemotherapy at first-line, most commonly Gemcitabine/Docetaxel or Adriamycin/Ifosphamide. While Gemcitabine/Docetaxel was the most preferred in the second line, different regimens were pursued in the third and later lines of therapy, including Pembrolizumab, Pazopanib, and stem cell transplant. Five out of 6 patients in the CD-related FDCS group received either adjuvant radiation or chemotherapy, which led to complete remission during the follow-up periods. The median follow-up was 22.4 months for the whole population. There was a trend for better OS and PFS among CD-related FDCS patients. The respective 2-year OS rates were 100% and 66.7%, and 2-year PFS rates were 57.1% and 43.1% for CD-related FDCS and FDCS-only patients, respectively. Conclusions: This study provides novel insights into clinicopathologic differences and survival trends for FDCS. Our data would suggest a less aggressive disease course among CD-related FDCS, which implies the need for different treatment strategies for CD and non-CD-related FDCS. Further research is warranted to elucidate these mechanisms, such as multi-omic analysis on benign FDC proliferation in the microdissected UCD areas and the adjacent FDCS cells to determine factors associated with progression to sarcoma.