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Abstract Background Chimeric-antigen-receptor (CAR) T-cell therapy has transformed outcomes for relapsed or refractory hematologic malignancies, yet early identification of patients at highest risk for death remains elusive. A prognostic model that leverages only the information routinely available at the time of CAR-T evaluationcould guide pre-infusion counseling, intensity of follow-up, and resource allocation. Methods We analyzed a prospectively maintained cohort of CAR-T recipients treated at Mayo Clinic to develop and test our model. For each patient, data (vital signs, lab results, cardiac assessments [ECG and echocardiography], and PET/CT images) from initial CAR-T evaluation (up to 60 days prior to CAR-T infusion) was considered. Vital signs and labs were left un-imputed, while ECG, echocardiographic parameters, and PET/CT features were forward-filled from the preceding 60 days. Each patient-day was labeled as “outcome present” or “no outcome,” enabling supervised training of gradient-boosting models to predict overall survival (OS) at 6 months post CAR-T infusion. Model performance was evaluated using the area under the ROC curve (AUC) with 10,000-fold bootstrapping with data shuffling between each iteration to derive confidence intervals for stability. To enhance interpretability, we also developed a simplified model using the top 19 features (determined by Shapley value-based importance), aiming to preserve predictive accuracy with a smaller feature set. Results A total of 570 CAR-T cell treated patients were included in this study (476 patients in the training cohort and 94 patients in the validation cohort). The median age was 64 years and 61% males. The primary diagnoses were B-cell lymphoma (324 patients) and multiple myeloma (246 patients). A total of 4,851 individual vital-sign readings, 11,781 laboratory measurements were included. PET/CT images were available in 318 patients. The ML model demonstrated high discriminative ability for predicting OS at 6 months post CAR-T infusion. Vital signs alone produced a mean AUC of 0.63; radiomics features alone produced a mean AUC of 0.71, while laboratory tests alone produced a mean AUC of 0.84. The features most contributory to each single-modality model were then combined into a simplified multimodal model with a total of 19 features, which produced a mean AUC of 0.87, with a 95% CI of 0.73 - 0.97. The 19 features included in the simplified model were: LDH, ferritin, uric acid, eosinophils, fibrinogen, D-dimer, heart rate, mean arterial blood pressure, QTc, QT interval, and the radiomics features of sphericity, first-order Kurtosis, first-order mean, first-order energy, first-order total energy, shape maximum2D diameter (sagittal plane), SUV CoV, SUVp90, shape flatness. This multimodal predictive model was then applied to the validation cohort (uninvolved with model training or testing), which produced an AUC of 0.93, with a 95% CI of 0.84 - 0.98. Conclusions Our ML-driven approach successfully predicts overall survival 6 months post CAR-T infusion, highlighting those individuals at most risk of poor outcomes at the time of CAR-T evaluation. The strong performance of the multimodal version of the model suggests that each data domain contributes complementary resolving power, and by including novel data types, such as PET CT radiomics features, the most accurate predictions could be realized. By providing accurate, near-real-time risk stratification for poor outcomes within 6 months of CAR-T infusion, the model could facilitate proactive patient management. Prospective studies of the integration of this ML model into CAR-T treatment workflows will be crucial to confirm its clinical benefits and to facilitate its adoption in practice.

Abstract Background Neurolymphomatosis (NL) is a rare and frequently underrecognized manifestation of lymphoma, characterized by infiltration of peripheral or cranial nerves by malignant lymphocytes. Limited data exist to guide optimal management. We present the largest single-enterprise (included the 3 Mayo Clinic sites) cohort to date, evaluating disease characteristics, treatment patterns, and outcomes in patients (pts) with NL. Methods We conducted a retrospective analysis of pts ≥18 years (yrs) diagnosed with clinical, radiographic, or biopsy-confirmed NL at Mayo Clinic between January 2002 and December 2024. Baseline characteristics were compared using independent t-tests for continuous variables and Fisher's exact or Pearson's chi-square tests for categorical variables. Primary endpoints were overall survival (OS) and progression-free survival (PFS). Objective response rate (ORR) was a secondary endpoint. Kaplan–Meier methods, log-rank tests, and Cox proportional hazards regression were used to assess survival outcomes and associated factors. Results We included 149 pts. Median age at diagnosis was 64 yrs (range 22–83), and 23% were female. Most presented with stage IV disease (89%), and NL was part of the initial lymphoma presentation in 42% (primary NL). Diagnostic confirmation was based on histopathology and imaging in 55%, imaging alone in 26%, histopathology alone in 16%, and clinical features in 4%. Diffuse large B-cell lymphoma was the most common histology (61%), followed by marginal zone lymphoma (7%), and T-cell lymphoma (7%). Clinical presentation included painful neuropathy (65%), concurrent CNS involvement (37%), systemic disease (43%), elevated LDH (46.9%), and ECOG ≥2 (38%). Pattern of involvement included cranial nerves (29%), peripheral nerves (28%), and spinal nerve roots (27%). Median follow-up was 92 months (95% CI, 63–119). Among 137 treatment-evaluable pts, first-line regimens included methotrexate-based (MTX) (62%), bendamustine-based (B) (11%), cytarabine-based (Ara-C) (4%), and rituximab-based (R) (excluding MTX, B, or Ara-C) (15%) therapies. Radiation was used in 18%, and 21% underwent autologous stem cell transplant (ASCT). Among 103 response-evaluable pts, the ORR was 67% (52% complete response [CR], 16% partial response [PR]). ORRs by regimen were 78% (MTX), 92% (B), and 86% (R). On univariate analysis, primary NL (OR 4.3) and frontline ASCT (OR 8.47) were associated with higher odds of response (p<0.05), while ECOG ≥2 (OR 0.24) and localized disease (OR 0.33) were associated with lower odds. On multivariable analysis (MVA), primary NL (OR 5.0 [1.5–12.1], p=0.02) and ECOG >1 (OR 0.2 [0.06–0.79], p=0.018) remained significant predictors of response. Median PFS was 13 months (95% CI, 9–36), with a 2-yr PFS of 43% (95% CI, 35–53). On MVA, concurrent CNS involvement (HR 2.4, p=0.05), systemic disease (HR 2.7, p=0.02), and ECOG >1 (HR 2.4, p=0.02) were associated with inferior PFS, while primary NL was associated with improved PFS (HR 0.3, p=0.002). Patients undergoing frontline ASCT had a median PFS of 108 months (95% CI, 58–not reached) with a 7-yr PFS of 62% (95% CI, 46–84). Among those receiving second line and beyond (2+) therapy, 24 received MTX-based regimens, 10 received CAR-T, and 8 received tyrosine kinase inhibitors. Post-ASCT median PFS was 30 months (95% CI, 15–NR). Among CAR-T recipients, evaluable responses (n=8) included 4 CR, 1 PR, and 3 PD. Median OS was 56 months (95% CI, 29–133), with a 5-yr OS of 50% (95% CI, 41–60). On MVA, ECOG ≥2 (HR 2.5, p=0.02) predicted worse OS, while receipt of ASCT (HR 0.4, p=0.04) and primary NL (HR 0.5, p=0.04) were associated with improved OS. Conclusion This study represents the largest single-enterprise cohort of pts with NL, providing comprehensive insight into its clinical presentation, treatment patterns, and outcomes. Primary NL and preserved PS were independently associated with improved response rates and survival, while CNS and systemic involvement at diagnosis portended poorer PFS. MTX and bendamustine-based regimens achieved high ORR, and frontline ASCT was associated with significantly prolonged remission duration and OS. These findings highlight the prognostic importance of baseline disease burden and functional status, support the early incorporation of high-intensity regimens in eligible patients, and underscore the urgent need for prospective studies to guide evidence-based management in this rare and understudied population.

Abstract Introduction: Anti-CD19 chimeric antigen receptor T-cell (CART) therapy is feasible with an acceptable safety profile in older patients (pts) with relapsed/refractory (RR) large B-cell lymphoma (LBCL) (Tun et al, AJH 2024). However, immune effector cell-associated neurotoxicity syndrome (ICANS) is a frequent and challenging toxicity in older pts, and its characteristics and associated risk factors are not well defined. Methods: Seven centers participated in this retrospective study. Pts aged ≥65 years (yrs) with RR LBCL treated with a commercial CART product were included. Baseline characteristics, treatment, CART toxicity, and outcomes were collected. ICANS was graded by the ASTCT criteria in most pts. Cumulative incidences of ICANS were estimated using deaths/progressions as competing risks, and associations between incidences and variables were assessed by Gray's test. A 30-day landmark was set after infusion to reduce immortal time bias. Progression-free survival (PFS; time from the landmark to disease progression or death) and overall survival (OS; time from the landmark to death) were analyzed with the Kaplan-Meier method. Statistical analyses were done in JMP v18. Results: A total of 224 pts were included. Median age at infusion was 71 yrs (range 65–89; ≥80 yrs, 12%. 142 (63%) were male and 27 (13%) had an ECOG PS scale of ≥2. The median HCT CI was 1 (range 0–6). LDH was elevated in 110 (51%) pts, 23 (19%) had bulky disease ≥7 cm, 176 (82%) had advanced-stage, and 145 (71%) had extranodal disease. Median number of prior treatments was 2 (range 1–8), and 44 (20%) had prior bendamustine. Prior stem cell therapy was done in 47 (21%) pts (autologous stem cell transplant [SCT], n = 45; allogeneic SCT, n=2). Axicabtagene ciloleucel (axi-cel) was most frequently used (58%; n=131) followed by lisocabtagene maraleucel (liso-cel) (16%, n=36) and tisagenlecleucel (tisa-cel) (25%, n=57). Median duration of ICANS was 6 days (interquartile range [IQR] 3–11; range 1–303). Median time to ICANS onset was 6 days (IQR 3.8–8.0; range 0–24). The 30-day cumulative incidence of all grade ICANS was 50.9% (95% confidence interval [CI] 44.7–57.9) and grade ≥3 ICANS was 29.8% (95% CI 24.0–37.0). There was no significant difference in incidence of all grade (P=0.39) and grade ≥3 (P=0.49) ICANS as well as duration of ICANS (≥14 vs <14 days; P=0.08) according to the age groups (≥65–69 vs ≥70–74 vs ≥75–79 vs ≥80–89). In contrast, pts with an ECOG PS scale of ≥2 were associated with a higher incidence of all grade (30-day estimate, 66.7% vs 47.0%; P=0.02) and grade ≥3 ICANS (30-day estimate, 53.8% vs 25.6%; P=0.002). In addition, pts with an elevated LDH level had a higher incidence of grade ≥3 ICANS than those without (30-day estimate, 37.5% vs 18.8%;P=0.004). The incidence of ICANS varied among various CART products, with 30-day estimates of 64.9% vs 33.3% vs 29.8% (P<0.0001) for all grades and 40.1% vs 13.2% vs 18.0% (P=0.004) for grade ≥3 ICANS in pts treated with axi-cel vs tisa-cel vs liso-cel, respectively. A trend toward higher grade ≥3 ICANS was seen in pts treated with ≥3 prior lines than those treated with 2 or 1 (30-day estimate, 35.7% vs 28.1% vs 10.5%; P = 0.07). ICANS was managed with steroids in 47 (41%) pts, levetiracetam +/- other agents in 46 (40%) pts, biologic agents +/- other drugs in 15 (13%) pts, and supportive care in 6 (5%) pts. Median follow-up from the 30-day landmark post-infusion was 17.2 months (95% CI 14.2–22.4). Median PFS was 10.5 months (95% CI 5.7–18.2) and OS was 18.2 months (95% CI 13.3 vs 27.5). There was no difference in PFS and OS in pts who experienced ICANS vs no ICANS (median PFS 14.7 vs 10.1 months; P=0.65 and median OS 18.2 vs 24.7 months; P=0.49). However, there was a trend toward inferior PFS and OS in pts who experienced high-grade ICANS compared to those who had grade 0-2 ICANS (median PFS 9.2 vs 21.2; P=0.14 and median OS 11.7 =vs 22.9; P=0.39). Conclusions: This large study of older pts with RR LBCL demonstrated acceptable risks of ICANS, comparable to that in pivotal registration trials, with a relatively higher rate of grade ≥3 ICANS. The risks of ICANS were similar regardless of patient age, including those aged ≥80 yrs, but different among CART products. Similar to younger pts, high tumor burden disease and poor performance status at CART infusion were associated with higher risks of ICANS. A comprehensive neurologic and frailty assessment is warranted to identify suitable CART candidates.

Abstract Background: De novo secondary central nervous system (CNS) lymphoma (SCNSL), characterized by concurrent systemic and CNS aggressive B-cell lymphoma at diagnosis, is a rare entity with a dismal prognosis. The prognostic significance of the initial anatomical compartment of CNS involvement (parenchymal vs. leptomeningeal) is not well-defined. We sought to analyze outcomes based on CNS localization in a single-institution cohort. Methods We retrospectively reviewed 34 patients with de novo SCNSL (including diffuse large B-cell lymphoma [DLBCL], high-grade B-cell lymphoma, not otherwise specified (HGBCL NOS), and double-/triple-hit lymphoma) treated at the Mayo Clinic between 2002 and 2025. Clinicopathological features, radiologic findings, treatment details, and survival outcomes were abstracted from the medical records. Patients were categorized by the primary site of CNS involvement. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method, and groups were compared with the log-rank test. Results The study cohort had a median age of 61.5 years (range 19-79) and a median International Prognostic Index score of 3 (range 2-4). Pathological subtypes included double-/triple-hit lymphoma (n=14, 41.2%), non-germinal center B-cell like (non-GCB) DLBCL (n=11, 32.4%), germinal center B-cell like (GCB) DLBCL (n=8, 23.5%), and HGBCL NOS (n=1, 2.9%). Among patients with available data, 14 (43.8%) were positive for MYC rearrangement, 13 (54.2%) for BCL2 rearrangement, and 10 (45.5%) for BCL6 rearrangement. First-line regimens received by patients included MR-CHOP (n=18, 52.9%), DA-R-EPOCH (n=5, 14.7%), combined CODOX-M/IVAC (n=4, 11.7%), R-CHOP with intrathecal methotrexate (n=3, 8.8%), miscellaneous therapies (n=3, 8.8%), and MRT (n=1, 2.9%). The complete response rate was 58.8% (n=20). Intrathecal chemotherapy was administered to 61.8% of patients, and consolidation with autologous stem cell transplant was performed in 35.3%. Based on the CNS compartment involved, de novo SCNSL (DN-SCNSL) were classified into two subtypes: the leptomeningeal subtype, defined as leptomeningeal involvement with or without parenchymal CNS disease (LM-DN-SCNSL; n=22, 64.7%), and the parenchymal subtype, defined as parenchymal-only CNS involvement (P-DN-SCNSL; n=12, 35.3%). Parenchymal disease was multifocal in 75% of cases, supratentorial in 58.3%, and associated with a midline shift in 30%. Although no tested factors (including pathological subtype, age, sex, and bone marrow involvement) were significantly associated with the anatomical compartment, a non-significant trend was noted for BCL6 rearrangement to be more common in the leptomeningeal group (8/13, 61.5%) than the parenchymal group (2/8, 25.0%) (P = 0.18). Survival outcomes were analyzed for both anatomical and pathological classifications. For the parenchymal versus leptomeningeal cohorts, 2- and 5-year Overall Survival (OS) rates were 75.0% vs. 45.1% and 41.0% vs. 38.7%, respectively (P = 0.34). For Progression-Free Survival (PFS), the 2- and 5-year rates were 48.6% vs. 32.5% and 29.2% vs. 26.0%, respectively (P = 0.53). The 2-year OS rates by pathological subtype were 81.8% for non-GCB DLBCL, 45.8% for DHL/THL, and 37.5% for GCB DLBCL (P = 0.27). Survival outcomes (OS/PFS) were not significantly associated with patient age, sex, pathological subtype, or anatomical compartment. Conclusion DN-SCNSL can be anatomically classified into two subtypes: LM-DN-SCNSL and P-DN-SCNSL. While a prognostic trend favoring the parenchymal subtype was observed, the difference did not achieve statistical significance, a finding likely attributable to the small cohort size. This classification may hold clinical utility for guiding risk stratification, and larger studies are needed to validate these findings and identify the most optimal treatments for each subtype of DN-SCNSL.

Abstract Background Primary central nervous system lymphoma (PCNSL) is a rare but aggressive non-Hodgkin lymphoma with limited prospective data to guide optimal therapy. This study evaluates real-world treatment patterns and survival outcomes using a large national cohort. Methods We analyzed data from the National Cancer Database (NCDB) for patients diagnosed with PCNSL between 2004 and 2020. Baseline demographics and treatment characteristics were analyzed using descriptive statistics. Survival outcomes were estimated using the Kaplan-Meier method and compared using log-rank tests. Multivariable Cox proportional hazards models were constructed to identify independent predictors of overall survival (OS). Results A total of 14,450 patients with PCNSL were included; 14,439 had first-line treatment data available, and 13,390 had survival data. Median age at diagnosis was 67 years (range 18-90), 49.2% were female, and 6.6% were African American. Chemotherapy alone was the modality of treatment for 81.6% (n=11,787), 12.2% (n=1,769) received chemoradiation, 3.8% (n=545) received chemotherapy and underwent autologous stem cell transplant (ASCT) but no radiation, and 2.4% (n=348) received radiation only. The median follow-up time was 73.5 months (95% CI 71.4-75.6), and the median OS for the group was 17.4 months (95% CI 16.2-18.6). Survival differed significantly by age group (median OS: <65 yrs, 46.1 months [95% CI 41.7 -50.6]; 65-79 yrs, 12.5 months [95% CI 11.2-13.7]; ≥80 yrs, 3.2 months [95% CI 2.9-3.5]; p<0.001), by year of diagnosis (median OS: 2004-2009, 11.0 months [95% CI 9.9-12.1]; 2010-2015, 20.0 months [95% CI 17.4-22.6], 2016-2020, 29.7 months [95% CI 26.0-33.4]; p<0.001), and by frontline treatment strategy (p<0.001). Patients treated with chemotherapy followed by ASCT had the longest median OS (not reached), while those receiving radiation alone had the poorest outcomes with a median OS of 3.9 months (95% CI 3.2-4.7); chemoradiation patients had a median OS of 31.8 months (95% CI 27.5-36.1), and chemotherapy only patients had a median OS of 13.9 months (95% CI 12.7-15.1)(p<0.001). African American patients had an inferior outcome with a median OS of 10.2 months [95% CI 7.2-13.1], compared to “other” races with a median OS of 36.9 months [95% CI 27.6-46.1] (p<0.001), although this is more similar to the median outcome for white patients (17.0 months [95% CI 15.8-18.3]). Treatment at an academic center (25.7 vs 11.0 months) and a high case-volume center (defined as >median number of cases per facility) (18.6 vs 10.5 months), and lower Charlson-Deyo comorbidity scores (CDS) (defined as CDS 0-1) (21.7 vs 6.8 months) were also associated with superior OS (p<0.001). In multivariable analysis, increasing age ( 65-79 y.o HR 1.60 [1.52-1.1.68], ≥80 y.o HR 2.95 [2.75-3.17]), CDS≥2 (HR 1.36 [1.28-1.44]), and African American race (HR 1.12 [1.02-1.24]) were adverse predictors of OS (all p<0.001), while treatment strategy (ASCT [HR 0.17], chemoradiation [HR 0.53], chemotherapy only [HR 0.68] compared to radiation alone), more recent year of diagnosis (2010-2015 [HR 0.81], 2016-2020 [0.70]), and treatment at an academic center [HR 0.81] remained predictors of superior OS (all p<0.001). Conclusion In this large national cohort of patients with PCNSL, treatment with chemotherapy followed by ASCT was associated with the most favorable survival outcomes. Patients treated with chemoradiation or multi-agent chemotherapy also demonstrated improved survival compared to those receiving radiation monotherapy or single-agent chemotherapy alone, respectively. Age, comorbidities, race, and treatment at academic centers were also significant independent predictors of OS. These findings highlight substantial disparities in outcomes and underscore the importance of optimizing treatment strategies, improving access to high-intensity therapies, and supporting timely referral to academic or high case-volume centers, particularly for younger and medically fit patients.

Abstract Zanubrutinib is a second-generation Bruton Tyrosine Kinase (BTK) inhibitor, FDA-approved for Mantle Cell Lymphoma (MCL), designed to be more selective and potentially better tolerated than first-generation agents like Ibrutinib. Progressive multifocal leukoencephalopathy (PML), a rare but severe complication, has not previously been reported with Zanubrutinib. We report a 74-year-old woman with a germline CHEK2 mutation and asymptomatic MCL (CD5+, cyclin D1+, Ki67 10–20%) diagnosed in 2016, managed with surveillance. In 2023, she was also diagnosed with localized breast cancer treated with lumpectomy and exemestane. Later that year, she developed new headaches. Brain MRI revealed diffuse bilateral pachymeningeal enhancement, suspicious for lymphomatous spread, without parenchymal involvement. By early 2024, follow-up imaging showed stable pachymeningeal enhancement with new scattered punctate right frontal subcortical lesions, coinciding with systemic MCL progression. Spinal imaging revealed epidural and bone marrow involvement; CSF was negative for malignancy. Zanubrutinib was initiated in March 2024. By August 2024, new bilateral frontal and parietal fuzzy hyperintense and faintly enhancing white matter lesions emerged, while prior punctate lesions regressed. Biopsy confirmed PML with JC virus DNA by in situ hybridization and absence of B-cell clonality. Zanubrutinib was discontinued. Follow-up imaging showed regression of lesions without new enhancement, consistent with immune reconstitution. The initial subcortical punctate lesions remained stable. In 2025, she was diagnosed with localized pancreatic adenocarcinoma, precluding cytotoxic therapy initially due to concern for PML reactivation. However, as of May 2025, neuroimaging remains stable, and patient was started on palliative gemcitabine/paclitaxel. This is the first reported case of PML associated with Zanubrutinib. It underscores the importance of vigilance for PML even in patients without overt immunosuppression, especially those with overlapping malignancies and treatment exposures in the correct clinical context.

Abstract Secondary central nervous system lymphoma (SCNSL) is defined as the diagnosis of CNS lymphoma diagnosed concurrently with systemic lymphoma or after prior treatment. Due to the poor prognosis associated with SCNSL, the lack of randomized trial data, and the need for international consensus guidelines, there is a high unmet need for effective therapy options for SCNSL. Here we present safety and efficacy data on 2 SCNSL patients treated with the combination of emavusertib and ibrutinib. Both patients had directly progressed on their prior BTKi treatment. One patient achieved an unconfirmed complete response (CRu) and remained on treatment for over 4 mos, while the other patient maintained stable disease (SD) with a 38% reduction in disease burden from baseline and was on treatment for more than 8 mos. The patient with a durable SD, who received 5 prior lines of therapy along with an ASCT, presented with 3 related AEs Grade ≥ 3 that were reversible and manageable. These included elevated ALT, AST, and bilirubin levels that resolved. The patient received emavusertib 300 mg BID and ibrutinib 560 mg QD. The CRu patient received 6 prior lines of therapy and experienced CK elevation, fatigue, hypoglycemia, sepsis, urinary retention, neutropenia, and constipation that resolved with either a dose reduction and/or supportive care. The initial dose for this patient was 150 mg emavusertib BID and ibrutinib 560 mg QD. Subsequently, the dose of emavusertib was decreased to 150 mg BID due to Grade 4 neutropenia, then increased to 200 mg AM and 150 mg PM once resolved. This patient achieved CRu within 60 days on treatment. The 2 patients presented here are supportive data for using the combination of emavusertib and ibrutinib in SCNSL.

ABSTRACT Newly diagnosed patients with non‐Hodgkin lymphoma (NHL) often have a history of other diseases, and these comorbidities can impact patient treatment and management options, as well as overall survival (OS). We developed the Lymphoma Epidemiology of Outcomes (LEO) comorbidity index (LCI) as a sum of 10 comorbidities adapted from the Self‐Report‐Generated Charlson Comorbidity Index (SRG‐CCI) for use in the LEO cohort, a national prospective study of newly diagnosed NHL. Of the 5502 participants with self‐reported comorbidity data, 3107 (56.4%) were male and the mean age at diagnosis was 60.9 years (range, 18–99 years). The LCI ranged from 0 to 6, with 48.6% having 0, 30.2% having 1, 21.2% having 2 or more comorbidities. With a median follow‐up of 62.4 months among surviving participants, 2099 patients had an event and 1219 died. Continuous LCI similarly predicted both 1‐year mortality (c‐statistic = 0.654) and OS (c‐statistic = 0.655), while it showed a weaker but still statistically significant predictive ability for lymphoma‐specific (c‐statistics = 0.617) and event‐free (c‐statistic = 0.574) survival. Participants with 1 (HR = 1.21, 95% CI 1.05–1.39) and 2+ (HR = 1.80, 95% CI 1.56–2.08) comorbidities had inferior OS compared to those with no comorbidities after adjustment for age and sex (c‐statistic = 0.654), and performance strengthened after adjustment for the International Prognostic Index (c‐statistic = 0.672). LCI predicted OS most strongly in marginal zone (c‐statistics = 0.748) and weakest in T‐cell (c‐statistic = 0.579) lymphoma. The cumulative incidence of death due to lymphoma, lymphoma treatment, and other causes all increased with increasing comorbidities, with the greatest increase observed for death due to other causes. The LCI performs comparable to other published comorbidity indices, supporting its use in the LEO cohort to better model real‐world outcomes and more generally providing an approach to implementing comorbidity indices in cancer survivorship cohorts.

Evaluation of T-cell receptor (TCR) β-chain constant region 1 (TRBC1) expression is an alternative T-cell clonality assessment method. However, evaluation of TRBC1 immunohistochemistry (IHC) for distinguishing mycosis fungoides (MF)/Sezary syndrome (SS) from reactive inflammatory infiltrates in skin is incomplete. We evaluated the utility of a novel dual TRBC1-CD3 IHC stain in skin biopsies with MF/SS (n=40), reactive (n=24), or atypical T-cell infiltrates indeterminant for MF/SS (n=9). Twenty of 24 reactive cases showed clear polytypic TRBC1 expression (median percent TRBC1 positivity among CD3-positive T cells [%TRBC1+] 50% in dermis, 42.5% in epidermis among all cases), while 34/40 MF/SS were clearly monotypic (%TRBC1+ either ≤20% or ≥85%) (sensitivity 85.0%, specificity 91.7%, positive predictive value 94.4%, negative predictive value 78.6%). Discordance between TRBC1 expression and diagnosis was associated with few neoplastic/monotypic T cells and/or lack of physical separation between neoplastic and non-neoplastic populations. Among patch/plaque MF/SS, TRBC1 showed similar diagnostic sensitivity (80.0% vs. 86.7%) and high categorical correlation (monotypic vs. not monotypic, 80%) with TCR gene rearrangement results. TRBC1 interpretation was reproducible, with ≥2/3 and 3/3 pathologists rendering identical interpretations in 100% and 86% of cases, respectively, after independent review and 100% agreement following collective review. Digital image analysis confirmed visual %TRBC1+ accuracy ( r =0.9749, P <0.0001). On the basis of these results, we propose %TRBC1+ cutoffs of <25% or >75% for establishing T-cell monotypia in skin. Considering such thresholds, TRBC1-CD3 evaluation facilitated diagnostic refinement in 7/9 (78%) atypical cases. Overall, TRBC1-CD3 IHC clearly and rapidly aids diagnosis of cutaneous T-cell proliferations.