Hwang, Steven R.

ABSTRACT Angioimmunoblastic T‐cell lymphoma (AITL) is an aggressive peripheral T‐cell lymphoma with poor outcomes, and the role of autologous stem cell transplantation (ASCT) as consolidation after frontline therapy remains controversial. We conducted a retrospective cohort study using the National Cancer Database, including adults diagnosed with AITL between 2004 and 2020 who received frontline systemic therapy. Patients were categorized as chemotherapy alone (Chemo) or chemotherapy followed by ASCT (Chemo + ASCT). To mitigate immortal time bias, prespecified landmark analyses were performed, with a 6‐month landmark analysis as the primary approach and a 9‐month landmark analysis as a sensitivity analysis. Multivariable Cox regression and propensity score weighting using inverse probability of treatment weighting for the average treatment effect were used to address measured confounding. Among 3996 patients receiving systemic therapy, 686 (17.2%) underwent ASCT. In the 6‐month landmark analysis, ASCT was associated with improved overall survival (HR, 0.53; 95% CI, 0.45–0.62; p < 0.001). Findings were consistent in the 9‐month landmark analysis (HR, 0.58; 95% CI, 0.49–0.69; p < 0.001) and IPTW‐adjusted model (HR, 0.51; 95% CI, 0.44–0.60; p < 0.001). In this large real‐world cohort, ASCT consolidation was consistently associated with improved survival in patients with AITL. Although treatment‐response data were unavailable and residual confounding cannot be excluded, these findings provide supportive real‐world evidence and warrant prospective studies with treatment‐timing and response data to better define patient selection.

Abstract The benefit of rituximab maintenance after first-line (1L) bendamustine-rituximab (BR) in patients with mantle cell lymphoma (MCL) remains uncertain, with inconsistent results from the phase 2 MAINTAIN trial and several retrospective studies. We conducted a large retrospective study at 27 US and Canadian academic centers to examine the benefit of rituximab maintenance after BR. A total of 911 patients received 1L BR between 2010 and 2020, and 703 had an objective response and no evidence of disease progression at the 3-month post-BR landmark. Among those, 394 (56%) received rituximab maintenance and 309 (44%) did not, with largely similar baseline patient and disease characteristics. In the landmark analysis, rituximab maintenance was associated with improved event-free survival (EFS; median, 49.9 vs 29.7 months; P&lt; .001) as well as overall survival (OS; median, 109.5 vs 74.2 months; P&lt; .001). The EFS and OS benefits were observed across most of the subgroups. EFS and OS differences were statistically significant in those who achieved a complete response to 1L BR (n = 590; median EFS, 62.7 vs 31.1 months [P&lt; .001]; median OS, 136.1 vs 75.3 months [P&lt; .001]), but the analysis among those who achieved a partial response to 1L BR was limited by the small sample size. These results provide additional evidence for the survival benefit of rituximab maintenance after BR in MCL and support its use in clinical trial design and routine practice.

Abstract Introduction: Adult T-cell leukemia/lymphoma (ATLL) is a rare blood disorder associated with human T-cell leukemia virus type 1 (HTLV-1) infection. It is generally categorized into four subtypes: smoldering, chronic, lymphoma, and acute. Given the heterogeneity of these subtypes, there is a significant difference in outcomes. Robust and contemporary epidemiological data are lacking for this rare disorder. We present a retrospective cohort study of patients with ATLL, utilizing the National Cancer Database (NCDB) to better characterize the epidemiology and survival trends in the United States. Methods: This is a retrospective cohort study using the NCDB to identify ATLL cases diagnosed from 2004-2020. Descriptive statistics summarized baseline characteristics, while chi-square tests assessed group differences. Overall survival (OS) was estimated using Kaplan-Meier analysis and compared using log-rank tests. Multivariable Cox proportional hazards models identified independent prognostic factors (p &lt; 0.05 considered significant). Results: A total of 635 patients were identified with ATLL, including 344 (54%) males and 291 (46%) females, with a median age at diagnosis of 59 years (range: 19-90). Most patients came from the Middle Atlantic (NY, NJ, PA) region (33%), followed by the South Atlantic (DC, DE, FL, GA, MD, NC, SC, VA, WV) region (20%) and the East North Central (IL, IN, MI, OH, WI) region (8%). Of the 635 patients, 335 (52%) were Black, 247 (39%) White, and 26 (4%) Asian. Sixty-five (10%) patients were of Hispanic origin. Over half of patients with ATLL (54%) had a median income below $46,000. International Prognostic Index (IPI) score was only available for 16 patients: three (19%) patients were in the high-risk group, 7 (43%) in the high-intermediate group, and 6 (37.5%) in the low-intermediate group. Treatment groups included 357 (56%) patients treated with chemotherapy and 29 (4.5%) who received radiation therapy. Thirty-three (5%) patients underwent hematopoietic stem cell transplant (HSCT), including 27 autologous and 16 allogeneic transplants. The median survival time in the cohort was 9 months (95% CI 7.3-10.7). One-year OS rate in the cohort was 43%, while 2-year and 5-year OS rates were 31% and 23.5%, respectively. Patients over the age of 65 had a significantly shorter median OS than those under 65 (4 vs. 11 months, p=0.001) and were significantly less likely to undergo HSCT (p&lt; 0.001). Black patients had significantly shorter median OS compared to White patients (7.8 months vs 13.3 months, p=0.014), despite similar treatment rates with chemotherapy and HSCT. Median OS appeared to improve over time, from 8 months in patients diagnosed between 2004-2009 to 10 months for those diagnosed between 2016-2020, although this was not statistically significant (p=0.145). Treatment with allogeneic HSCT was associated with significantly prolonged median survival, compared to those who did not receive transplant (50 months vs. 7 months, p&lt;0.05). Additionally, receiving chemotherapy and/or radiation compared to not receiving treatment was also associated with significantly prolonged median survival (p&lt;0.05). Patients treated in the Middle Atlantic region had a median survival of 8.8 months, compared to 23.2 months in the West South Central (AR, LA, OK, TX) region (p&lt; 0.001). Increased education and income levels were not significantly associated with improved survival. There were no significant differences in survival between males and females. Conclusions: We provide contemporary estimates on the epidemiology of ATLL. Factors associated with improved prognosis included undergoing HSCT, radiation, or chemotherapy. We report that increased age and Black race are negative prognostic factors. Regional differences in incidence and survival persist in the US. Our study findings underscore the need for increasing access to treatment, including HSCT for those who are good candidates. Additionally, there remains work to be done to address racial disparities in the care of patients with ATLL.

Abstract Background: Splenic Marginal Zone Lymphoma (SMZL) is a rare B-cell lymphoma with heterogeneous clinical behavior. Although typically indolent, survival outcomes are modestly inferior to those of other indolent lymphomas, with 5-year overall survival (OS) rates of 70–80% compared to 85–95% in follicular or nodal marginal zone lymphoma. Additionally, 5–10% of patients present with aggressive disease, highlighting the need for better prognostic tools and treatment strategies. While rituximab (RTX) has become central to SMZL management, often replacing splenectomy as first-line therapy, it remains unclear whether survival outcomes have improved during this era of increased RTX use. We conducted a national analysis to characterize treatment patterns, prognostic factors, and survival trends over time. Methods: We conducted a retrospective cohort study of SMZL cases diagnosed between 2004 and 2020 using the National Cancer Database (NCDB). Descriptive statistics characterized baseline features. OS was estimated via Kaplan-Meier methods and compared using log-rank tests. Cox proportional hazards models assessed prognostic factors. To evaluate changes in survival over time, we stratified cases by year of diagnosis into early (2004–2009), mid (2010–2014), and recent (2015–2020) RTX-era cohorts. Differences in survival between eras were compared using the log-rank (Mantel–Cox) test. Results: Among 7,228 patients with SMZL, treatment data were available for 7,176 (99.2%). Median age at diagnosis was 69 years (IQR: 60 to 77), with 4.9% identifying as African American. Of 4,167 patients with stage data, 64% had advanced-stage (III or IV) disease. Among patients with available risk scores, 37% were classified as high-risk by IPI (4-5) and 43% had a Charlson-Deyo (CD) comorbidity score of 3 or higher. Treatment patterns included splenectomy alone in 1,381 patients (19%), RTX monotherapy in 2,068 (28.5%), and combined RTX and splenectomy in 3,727 (51.9%). Chemotherapy was administered to 1,834 patients (25%), radiation to 29 (0.4%), and autologous transplant to 3. Treatment modalities overlapped due to multimodal approaches; Patients undergoing splenectomy tended to be younger (≤65 years), have earlier-stage disease, lower CD scores, and low-risk IPI (all p &lt; 0.001). Sixty-eight percent received care at academic centers. Median follow-up was 130 months (95% CI: 123.2 to 136.4). Three- and five-year OS rates were 81.5% and 73.6%, respectively. Despite increased RTX use over time, no significant improvement in OS was observed across eras (log-rank p = 0.35). Survival varied significantly by treatment strategy (p &lt; 0.001). Patients who received neither RTX nor splenectomy had the poorest outcomes, with a median OS of 19.3 months (95% CI not estimable to 70.7). Splenectomy alone was associated with the longest median OS of 148.8 months (95% CI: 137.9 to 159.7), though this likely reflects favorable patient selection. Median OS was not reached for RTX monotherapy patients, suggesting similarly favorable, if not superior long-term outcomes. Combined RTX and splenectomy were associated with similarly prolonged survival (median OS 119.4 to 120.6 months). Addition of chemotherapy in sequential treatment did not significantly affect OS (121 vs. 131 months; p = 0.07). On multivariable analysis, factors independently associated with inferior OS included older age at diagnosis (HR 1.07; 95% CI: 1.06–1.08; p &lt; 0.001) and higher CD comorbidity score (HR 1.29; 95% CI: 1.18–1.42; p &lt; 0.001). In contrast, female sex (HR 0.66; 95% CI: 0.56–0.78; p &lt; 0.001), treatment at an academic center (HR 0.84; 95% CI: 0.71–0.99; p = 0.04), and receipt of RTX (HR 0.48; 95% CI: 0.32–0.74; p &lt; 0.001) were associated with prolonged OS. Conclusion: In this large national cohort of SMZL, receipt of RTX, alone or with splenectomy, was associated with improved OS. Favorable prognostic factors included younger age, female sex, lower comorbidity burden, and treatment at academic centers. However, despite greater RTX use over time, population-level survival in the recent RTX era has not significantly improved, likely reflecting poor outcomes in relapsed or refractory disease. These findings highlight the need to optimize frontline therapy and develop novel strategies to improve long-term outcomes in SMZL.

Abstract Background The benefit of high-dose chemotherapy and autologous stem cell transplantation (ASCT) as a consolidation strategy after initial chemotherapy in peripheral T-cell lymphoma (PTCL) is currently unclear, and a randomized trial (EA4232/PTCL-STAT) to answer this question is currently underway. Angioimmunoblastic T-cell lymphoma (AITL) is a rare, aggressive subtype of nodal PTCL with poor prognosis and unique features. Here, we report a large-scale, real-world evidence on the role of ASCT in frontline AITL management. Methods We analyzed a national cohort of 5,827 patients diagnosed with AITL between 2004 and 2020 from the National Cancer Database (NCDB). Baseline demographic, clinical, and socioeconomic characteristics were assessed. Treatment modalities included chemotherapy alone, chemotherapy with ASCT, and no treatment. Overall survival (OS) was evaluated using Kaplan-Meier method and multivariable Cox proportional hazards regression. Propensity score matching (PSM) was performed to validate ASCT's treatment effect. Results Among patients with complete treatment information (n = 5,224), the median age at diagnosis was 68 years (range 20–90). Frontline treatments included chemotherapy alone (68.6%, n = 3,584), chemotherapy with ASCT (14.6%, n = 761), and no treatment (16.8%, n = 879). Compared with patients who did not receive ASCT, those who underwent ASCT were significantly younger (median 60.0 vs 68.0 years), more frequently treated at academic centers (81.5% vs 57.9%, p &lt; 0.001), and more likely to reside in areas with higher educational attainment (p &lt; 0.001). They exhibited lower Charlson-Deyo comorbidity scores (CDS), with a higher proportion having a score of 0 (82.8% vs 73.6%, p &lt; 0.001), and were more likely to have advanced-stage disease (93.0% vs 86.9%, p &lt; 0.001). Furthermore, a higher proportion of patients who received ASCT were diagnosed in more recent years (p &lt; 0.001). Sex, race, and IPI score distribution showed no significant baseline differences. Median follow-up time was 81.1 months (95% CI: 77.4–84.9), and the median OS was 23.3 months (95% CI: 21.3–25.2) for the entire cohort. For patients receiving chemotherapy with ASCT, the median OS was 139.2 months (95% CI: 104.2–174.2). In comparison, chemotherapy alone yielded a median OS of 23.6 months (95% CI: 21.4–25.8), while patients who received no treatment had a median OS of 4.0 months (95% CI: 2.7–5.2); overall p &lt; 0.001. Median OS also significantly improved with more recent diagnosis eras: 20.1 months for patients diagnosed in 2004–2009 (95% CI: 16.8–23.4), 23.9 months for those diagnosed in 2010–2015 (95% CI: 21.0–26.7), and 26.7 months for patients diagnosed in 2016–2020 (95% CI: 23.1–30.4) (p &lt; 0.001). Analyses consistently demonstrated longer median OS in female patients (27.5 vs. 20.7 months in males, p &lt;0.001), and in patients treated at academic centers (27.5 vs. 16.4 months at non-academic centers, p &lt; 0.001). Median OS varied by race (White: 24.0 months vs. Black: 15.2 months vs. Others: 30.3 months; p = 0.017). Patients with higher household income and higher educational attainment experienced significantly improved survival (p = 0.005 and p = 0.017, respectively). Patients with early-stage disease, lower IPI scores, and lower CDS also showed significantly longer survival (p &lt; 0.001 for all comparisons). Multivariate Cox regression showed that chemotherapy with ASCT significantly reduced mortality risk compared to chemotherapy alone (HR = 0.438, 95% CI: 0.364–0.527, p &lt; 0.001). No treatment significantly increased mortality risk (HR = 1.941, 95% CI: 1.634–2.305, p &lt; 0.001). PSM analysis further validated that chemotherapy with ASCT significantly lowered mortality risk compared to chemotherapy alone (HR = 0.608, 95% CI: 0.503–0.736, p &lt; 0.001), after matching for age at diagnosis, sex, race, income, education level, academic center, stage, CDS, and diagnosis era. Conclusion This large-scale, real-world analysis suggests that chemotherapy followed by ASCT is associated with significantly improved overall survival in patients with AITL, supported by unadjusted Kaplan-Meier analysis, adjusted multivariate Cox regression, as well as PSM analysis. These data support ASCT as an important consolidation strategy for AITL in real-world practice.

Abstract Primary central nervous system lymphoma (PCNSL) is a rare form of non-Hodgkin lymphoma involving the brain, cerebrospinal fluid, or retina/vitreous without systemic involvement. Induction with high-dose methotrexate (HD-MTX) followed by consolidation with autologous stem cell transplant (auto-SCT) has become the standard treatment paradigm for most patients. However, limited data are available regarding the efficacy of a maintenance approach with HD-MTX. Herein, we retrospectively reviewed the characteristics and outcomes of 148 patients diagnosed with PCNSL between October 2010 and June 2022, who underwent HD-MTX–based induction therapy followed by either auto-SCT consolidation (n = 70) or HD-MTX maintenance therapy (n = 37). At a median follow-up time of 4.5 years, the progression-free survival (PFS) was 8.3 years and the overall survival (OS) was not reached. Compared to patients who underwent auto-SCT, patients who received maintenance HD-MTX had a higher median age at diagnosis of 72 vs 62 years and a trend toward higher proportion of patients being Eastern Cooperative Oncology Group 2 or higher (41% vs 29%). At 5-years postinduction treatment initiation, the PFS rates in the auto-SCT cohort and HD-MTX maintenance cohort were 74.6% and 72.6%, respectively, and the OS rates were 76.0% and 82.4%, respectively. Overall, there was no significant difference in PFS or OS based on postinduction management strategy. Our data suggest that maintenance HD-MTX may be a reasonable, time-limited treatment strategy for patients with PCNSL responding to initial induction therapy.

Background: Splenic marginal zone lymphoma (SMZL) is a rare indolent disease with a median overall survival (OS) of more than 10 years, although a proportion of patients may develop aggressive histology transformation. In a previous report from this large, international dataset, the 10-year cumulative incidence of transformation was 17% (95% 13-21) and in another study of 186 patients, the 10-year cumulative incidence was 14%Click or tap here to enter text.. In this report, we focus on risk factors for transformation as well as clinical characteristics and outcomes of transformed SMZL (tSMZL). Patients and methods: Adults diagnosed with SMZL in 2000-2018 were identified through regional or nationwide population-based registries or from hospital registries. Only patients likely to have SMZL as defined by Matutes et al. were included. Those with discordant lymphoma and/or transformation at diagnosis were excluded. Medical records were reviewed by local clinicians with experience in hematology/oncology, and detailed information on clinical characteristics, treatment lines, and outcomes was collected. Only histologically confirmed high-grade transformations (HT) were included. OS was defined as the time from transformation to death or censoring at last follow-up. Additional analyses stratified by treatment exposure prior to HT and treatment of HT were conducted. Multivariable Cox analyses were performed to determine clinicopathological features associated with transformation and OS. Results: Out of 940 patients with SMZL, 111 developed HT during a median follow-up of 9.1 years. The median time from diagnosis to HT was 3.4 years with an interquartile range of 1.6-7.4 years. Median age at HT was 71 years. Patients with HT shared similar baseline characteristics to those without in terms of age at diagnosis (66.4 vs 67.6), f:m ratio (1.5 vs 1.1) and ECOG ³2 (7.2% vs 7.4%). The 5-yr OS from the time of HT was 42% (CI 95%, 32-54). Of the 111 patients with tSMZL, a complete treatment history from SMZL diagnosis until HT was available for 88 included in the following analyses. By the time of HT, 46 had not received any prior systemic therapy (37 only splenectomy, 9 no therapy), 6 patients had received rituximab alone or combined with splenectomy, and 36 patients had received chemotherapy alone or as part of combined modality treatment. In a uni- and multivariable models for HT, we assessed age, treatment at diagnosis, sex, extra-hilar lymphadenopathy, and extranodal involvement. In both the uni- and multivariable model, age &gt;70 (HR 1.9, 95% CI: 1.1-3.4), immediate treatment including splenectomy (HR 2.0, 95% CI: 1.05-3.6), and extra-hilar lymphadenopathy (HR 1.9, 95% CI: 1.1-3.3) were associated with higher HT hazard, while extranodal involvement (HR 0.23, 95% CI: 0.06-0.84) was associated with a lower HT hazard. At the time of first-line treatment, multivariable analysis revealed similar results and with no association between risk of transformation and treatment strategy (i.e splenectomy alone, rituximab monotherapy or chemotherapy with /without rituximab or splenectomy, and other). At the time of HT, patients who had been previously treated with chemotherapy had an inferior 5-year OS of 24% (95%CI: 13-44%) versus 54% (95%CI: 41-71%) for those who had not received chemotherapy prior to HT. In contrast, there was no difference in the survival of patients that transformed less than or more than 24 months from diagnosis with 5-year OS after HT of 35% (95%CI 20-60%) and 45% (95%CI, 33-61%) respectively. In a multivariable Cox regression analyses of age at time of HT, sex, time since last treatment &lt;24 months, chemo-exposure in previous treatment lines and anthracycline-containing therapy (+/-R) at the time of HT, only prior chemo-exposure was borderline associated with poorer OS (HR 1.8, 95%CI: 0.9-3.5). Conclusion: Patients with SMZL face a notable risk of developing tSMZL over time. Patients in need of immediate treatment at first SMZL diagnosis, age &gt;70 and extrahilar lymphadenopathy had a higher risk of tSMZL and outcomes at the time of HT were poor if patients had been exposed to prior chemotherapy after adjustment for age, sex, and time since last treatment.

Background Mantle cell lymphoma (MCL) is more common in males, with a male to female ratio of approximately 3:1. However, it is unclear whether disease characteristics and survival outcomes differ by sex. Additionally, the impact of race and ethnicity in MCL is understudied due to underrepresentation of minorities in clinical studies and trials. In this study, we utilized the National Cancer Database (NCDB) to examine patient and disease characteristics and survival outcomes of MCL by sex, race and ethnicity. Methods Patients diagnosed with MCL in 2004-2020 were identified from NCDB. Patient and disease characteristics were compared between groups using Chi-squared tests. Overall survival (OS) analysis was performed using the Kaplan-Meier method and the Cox proportional hazards model. Results A total of 35,135 patients was included. The median follow-up was 83.0 months (95% CI 81.9-84.1). 24,980 (71.1%) patients were male and 10,155 (28.9%) were female. Females had more elderly (age ≥65: 65.9% vs 59.0%; p&lt;0.001), lower Charlson-Deyo Score (CDS ≥2: 7.0% vs 8.6%; p&lt;0.001) and fewer stage III-IV diagnoses (80.5% vs 82.6%; p&lt;0.001). Females were less likely to receive upfront treatment (80.7% vs 85.3%; p&lt;0.001), treatment at academic centers (36.8% vs 40.9%; p&lt;0.001) or transplant (11.0% vs 13.7%; p&lt;0.001). Compared to males, females were more likely to live in metropolitan areas (83.7% vs 81.6%; p&lt;0.001), had similar incomes, had more Medicare (60.4% vs 53.1%) and fewer private insurance (33.2% vs 38.6%; p&lt;0.001). Female patients had better OS, with a median OS of 76.0 (95% CI 72.4-79.6) vs 67.8 months (95% CI 65.9-69.6; p&lt;0.001). In the multivariable Cox model adjusting for age, race, ethnicity, CDS, stage, upfront treatment (vs surveillance or no treatment), facility (academic vs nonacademic), transplant, residence (metropolitan vs urban or rural) and insurance, female sex remained associated with superior OS (HR 0.84, 95% CI 0.793-0.890; p&lt;0.001). For race, 32,399 (92.2%) patients were White, 1,465 (4.2%) were Black, 942 (2.7%) were others and 329 (0.9%) were unknown. Compared to White patients, Black patients had fewer elderly (52.9% vs 61.7%; p&lt;0.001), higher CDS (≥2: 11.4% vs 7.9%; p&lt;0.001), similar stage III-IV (80.7% vs 82.1%; p=0.276) and upfront treatment (84.7% vs 84.0%; p=0.074), were more likely to be treated at academic centers (50.6% vs 38.9%; p&lt;0.001), were less likely to receive transplant (11.1% vs 13.0%; p=0.042), were more likely to live in metropolitan areas (91.0% vs 81.5%; p&lt;0.001), had lower income, had more uninsured (4.4% vs 2.0%) and Medicaid (9.8% vs 3.7%) and fewer Medicare (47.4% vs 56.0%; p&lt;0.001). Black and White patients had similar OS, with a median of 67.9 (95% CI 57.5-78.2) vs 69.6 months (95% CI 67.8 vs 71.3; p=0.697). In the multivariable Cox model, Black vs White race was not associated with OS (HR 1.086, 95% CI 0.952-1.240; p=0.219). For ethnicity, 31,717 (90.3%) patients were non-Hispanic, 1,894 (5.4%) were Hispanic and 1,534 (4.3%) were unknown. Hispanics had fewer elderly (51.3% vs 61.5%; p&lt;0.001), lower CDS (≥2: 6.4% vs 8.2%; p=0.018), similar stage III-IV (81.2% vs 82.1%; p=0.467), were more likely to receive upfront treatment (86.0% vs 83.9%; p&lt;0.001), more likely to be treated at academic centers (49.9% vs 39.5%; p&lt;0.001), equally likely to receive transplant (13.0% vs 13.1%; p=0.943), more likely to live in metropolitan areas (95.4% vs 81.6%; p&lt;0.001), had lower income, had more uninsured (9.6% vs 1.8%) and Medicaid (15.2% vs 9.6%) and fewer Medicare (40.3% vs 55.9%; p&lt;0.001). Hispanics had better OS, with a median OS of 84.4 (95% CI 71.7-97.1) vs 70.5 months (95% CI 68.7-72.2; p&lt;0.001). However, in the multivariable Cox model, Hispanic ethnicity was not associated with OS (HR 0.952, 95% CI 0.839-1.080; p=0.448). Conclusion This study is the first of its scale to demonstrate that female MCL patients have superior survival outcomes compared to males. It also demonstrated that neither Black race nor Hispanic ethnicity appears to be associated with worse survival outcomes. Despite its size, the NCDB is limited in the treatment information and disease characteristics it provides, including MIPI score, Ki-67, blastoid/pleomorphic morphology, and TP53 status. Thus, additional real-world dataset studies are needed to gain a deeper understanding of potential differences in sex, race and ethnicity with regards to disease characteristics and survival outcomes.

Abstract Little is known about risk factors for central nervous system (CNS) relapse in mature T-cell and natural killer cell neoplasms (MTNKNs). We aimed to describe the clinical epidemiology of CNS relapse in patients with MTNKN and developed the CNS relapse In T-cell lymphoma Index (CITI) to predict patients at the highest risk of CNS relapse. We reviewed data from 135 patients with MTNKN and CNS relapse from 19 North American institutions. After exclusion of leukemic and most cutaneous forms of MTNKNs, patients were pooled with non-CNS relapse control patients from a single institution to create a CNS relapse–enriched training set. Using a complete case analysis (n = 182), including 91 with CNS relapse, we applied a least absolute shrinkage and selection operator Cox regression model to select weighted clinicopathologic variables for the CITI score, which we validated in an external cohort from the Swedish Lymphoma Registry (n = 566). CNS relapse was most frequently observed in patients with peripheral T-cell lymphoma, not otherwise specified (25%). Median time to CNS relapse and median overall survival after CNS relapse were 8.0 and 4.7 months, respectively. We calculated unique CITI risk scores for individual training set patients and stratified them into risk terciles. Validation set patients with low-risk (n = 158) and high-risk (n = 188) CITI scores had a 10-year cumulative risk of CNS relapse of 2.2% and 13.4%, respectively (hazard ratio, 5.24; 95% confidence interval, 1.50-18.26; P = .018). We developed an open-access web-based CITI calculator (https://redcap.link/citicalc) to provide an easy tool for clinical practice. The CITI score is a validated model to predict patients with MTNKN at the highest risk of developing CNS relapse.