Abstract Background: Mantle cell lymphoma (MCL) is a distinct type of non-Hodgkin’s Lymphoma characterized by being incurable with a low response rate and short progression free survival when treated with conventional chemotherapy agents. Lenalidomide (Revlimid®), an immunomodulatory drug, is approved for the treatment of relapsed/refractory multiple myeloma and myelodysplastic syndromes associated with a del(q5) cytogenetic abnormality. Lenalidomide has also shown activity in chronic lymphocytic leukemia and cutaneous T-cell lymphoma. Aim: To determine the activity and safety of lenalidomide in relapsed/refractory MCL. Methods: Patients with relapsed/refractory MCL and measurable disease ≥ 2 cm after at least 1 prior treatment regimen were eligible. Patients received 25 mg lenalidomide orally once daily on Days 1–21 every 28 days and continued therapy for 52 weeks as tolerated or until disease progression. Response and progression were evaluated using the IWLRC methodology. Results: Fifteen patients with MCL were enrolled. Median age was 67 (45–84) and 7 were female. Median time from diagnosis to lenalidomide was 5.1 (0.7–12.7) years and median number of prior treatment regimens was 4 (2–6). Eight patients (53%) exhibited an objective response (1 complete response (CR), 1 complete response unconfirmed (CRu) and 6 partial responses (PR)), 2 had stable disease (SD) and 5 had progressive disease (PD). All eight responses were in eleven patients having a tumor burden < 50 cm2 and a time since last rituximab therapy of ≥ 230 days. No responses were achieved in four patients having a tumor burden ≥ 50 cm2 or a time since last rituximab therapy of < 230 days. Four of 5 patients (80%) with a prior stem cell transplant responded. Progression free survival [PFS] is 5.7 months and ongoing. Seven patients (47%) required at least one dose reduction with a median time to first dose reduction of 2.3 months (1.2–4.9). Grade 4 adverse events were neutropenia (13%), thrombocytopenia (13%), and thromboembolism (13%). Most common Grade 3 adverse events were neutropenia (33%) and leukopenia (20%). Conclusion: Lenalidomide oral monotherapy produced a 53% response rate in relapsed/refractory MCL with manageable side effects.
Host Genetic Variation in the Cell Cycle and NF-κB Pathways and Overall Survival in Mantle Cell Lymphoma.
Abstract Background: Mantle cell lymphoma (MCL) is an incurable non-Hodgkin lymphoma. MCL is characterized by the chromosomal translocation t(11;14) leading to overexpression of cyclin D1 (CCND1), a regulator of the cell cycle. NF-κB plays a central role in key cellular processes, including cell cycle regulation and apoptosis, and it has been shown to be constitutively activated in MCL cell lines and in patient biopsy samples and to play a key role in the growth and survival of MCL cells. In an exploratory study, we evaluated the hypothesis that germline variation in candidate genes from the cell cycle and NF-κB pathways predict overall survival in MCL. Methods: We genotyped 235 SNPs from 29 cell cycle genes and 447 SNPs from 55 NF-κB genes in 39 MCL patients aged 38–64 years who participated in a population-based study conducted from 1998–2000 through the Surveillance, Epidemiology, and End Results (SEER) cancer registries in Detroit, Seattle, Iowa, and Los Angeles county. Tagging single nucleotide polymorphisms (SNPs) were selected from HapMap. Stage, presence of B-symptoms, first course of therapy, date of last follow-up, and vital status were derived from linkage to registry databases at each study site. To assess the statistical significance of a gene, we first used principal components analysis to capture the genetic variation of the SNPs within a gene. Cox proportional hazards analysis was then used to assess the association between the top principal components from a gene with overall survival. Results: Through early 2005, there were 22 deaths in 39 patients (56%). The median follow-up of the 17 surviving patients was 56 months (range 36–70). Eleven of the 55 genes (TNFSF14 p=0.0007, NF-κBIA p=0.003, IL1R2 p=0.01, TNFRSF25 p=0.02, TNFSF13B p=0.02, FAS p=0.03, TLR2 p=0.04, TNFSF10D p=0.04, TNFSF10 p=0.06, MAP3K2 p=0.06) in the NF-κB pathway were associated with overall survival. In the cell cycle pathway, only 3 of the 29 genes (CASP5 p=0.06, CASP9 p=0.09, BCL2 p=0.09) were associated with overall survival, and a previously reported SNP in CCND1 (rs603965) showed no association (p=0.5). Permutation p-values for observing at least this number of associated tests in each pathway due to chance (from multiple testing) was p=0.8 for the cell cycle pathway and p=0.03 for NF-κB pathway. The small sample size precluded multi-gene modeling. Conclusion: In a population series of MCL patients, we found suggestive evidence that host genetic variation in candidate NF-κB pathway genes affects overall survival. These results complement tumor expression data implicating this pathway in the pathogenesis of MCL. In addition, such findings further support the value of developing therapeutic targets from this pathway.
High Response Rate to Lenalidomide in Relapsed/Refractory Aggressive Non-Hodgkin’s Lymphoma with Prior Stem Cell Transplant.
Abstract Background: High dose chemotherapy with stem cell transplant is currently employed in relapsed/refractory aggressive Non-Hodgkin’s Lymphoma (NHL). Lenalidomide (Revlimid®), an immunomodulatory drug, has shown activity in hematological malignancies including relapsed/refractory multiple myeloma, chronic lymphocytic leukemia and cutaneous T-cell lymphoma. Aim: To determine the activity and safety of lenalidomide monotherapy in relapsed/refractory aggressive NHL following stem cell transplant (SCT). Methods: Patients with relapsed/refractory aggressive NHL with measurable disease ≥ 2 cm after at least 1 prior treatment regimen were eligible. Patients received 25 mg lenalidomide orally once daily on Days 1–21 every 28 days and continued therapy for 52 weeks as tolerated or until disease progression. Response and progression were evaluated using the IWLRC methodology. Results: Fourteen (29%) of the 49 patients enrolled into the study had a prior SCT. Median age was 61 (23–76) and 5 were female. Histology was diffuse large B-cell lymphoma [DLBCL] (n=5), follicular center lymphoma grade 3 [FL] (n=2), mantle cell lymphoma [MCL] (n=5) and transformed [TSF] (n=2). Median time from diagnosis to lenalidomide was 3.9 (1.1–31.4) years and median time from SCT to study entry was 1.9 (0.5–11.7) years. The median number of prior treatment regimens was 5 (2–8). Seven patients (50%) exhibited an objective response (1 complete response unconfirmed (CRu), and 6 partial responses (PR)), 5 had stable disease (SD) and 2 patients had progressive disease (PD). Six responses were in eight patients having a tumor burden < 50 cm2 and a time since last rituximab therapy of ≥ 230 days. One response was achieved in six patients having a tumor burden ≥ 50 cm2 or a time since last rituximab therapy of < 230 days. Four of 6 (67%) patients who had SCT as their last treatment prior to lenalidomide [median time from SCT to lenalidomide = 0.8 (0.5–4.8) years] responded. Progression free survival [PFS] is 4.5 months and ongoing. Six patients (43%) required at least one dose reduction with a median time to first dose reduction of 1.6 months (0.4–4.9). Two patients each (14%) had Grade 4 adverse events of neutropenia and thrombocytopenia. The most common Grade 3 adverse events were neutropenia (36%), thrombocytopenia (21%), and leukopenia (14%). Conclusion: Lenalidomide produced a 50% response rate with manageable side effects in relapsed/refractory aggressive NHL following stem cell transplant.
Non-Hodgkin’s Lymphoma in the Context of Antecedent Rheumatoid Arthritis: A Case Series from the Mayo Clinic and the Nebraska Lymphoma Study Group.
Abstract PURPOSE: Rheumatoid arthritis (RA) has been associated with an increased risk of non-Hodgkin’s lymphoma (NHL). We describe the characteristics of NHL patients with antecedent RA. METHODS: Records of the Nebraska Lymphoma Study Group (NLSG) registry between 1982–2004 and the Mayo Clinic lymphoma registry between 1988–1998 were systematically reviewed for RA diagnosis and classified by the quality of supporting evidence. We abstracted available follow-up data through July 1, 2004. Definite cases had either a documented RA diagnosis from a trained rheumatologist or met 4 of 7 American College of Rheumatology criteria. Probable RA cases had a non-rheumatologist diagnosis of RA in addition to one of the following: 1) radiographic joint erosions; 2) disease-modifying anti-rheumatic drug (DMARD) use or; 3) RA-associated deformities (i.e., ulnar drift, swan-neck deformities). Five-year overall survival (OAS), event-free survival (EFS), and rates of treatment response were determined. RESULTS: We identified 74 RA cases (54 definite and 20 probable) with concomitant NHL. These patients had a mean age of 67 + 8 years and were predominantly Caucasian (82%) and female (64%). Of the probable RA cases, a majority had documented DMARD use (n=17). Approximately half of the cases used methotrexate (55%) and were deceased (52%) by the common closing date. The most common NHL subtypes included B-DLCL (n=31), B-FL-1/B-FL-2 (n=12), B-FL-3 (n=6), and B-BL/B-BLL (n=4). Of the remaining 21 cases, most were of B-cell origin (n=13) and included B-EMZL (n=3), B-LPL (n=3), B-UCL (n=2), B-UCL-LG (n=2), B-DFL-2 (n=1), B-MCL (n=1), and B-SLL (n=1). The remaining NHL subtypes included NHL-NOS (n=7) or T-PTCL-LC (n=1). B-symptoms were present for 6 (19%) patients with B-DLCL and none of the patients with B-FL-1/B-FL-2. Complete response rates to NHL treatment were 48% in B-DLCL and 33% in B-FL-1/B-FL-2. For B-DLCL and B-FL-1/B-FL-2, respectively, the five-year OAS was 54% (95% CI 36%–69%) and 65% (95% CI 31%–85%) while the five-year EFS was 48% (95% CI 36%–69%) and 56% (95% CI 24%–79%). For all NHL cases the 5-year OAS was 58% (95% CI 47%–69%) and the 5-year EFS was 49% (95% CI 37%–59%). CONCLUSIONS: Lymphomas developing in the context of RA most often include diffuse large B-cell and follicular subtypes. Complete response rates to standard treatment for these major subtypes ranged from 33 to 48%. For RA patients developing NHL, five-year overall- and event-free survival rates are approximately 50%.
mTOR Inhibition for Relapsed or Refractory Hodgkin Lymphoma: Promising Single Agent Activity with Everolimus (RAD001).
Abstract Background: mTOR inhibition has produced responses in mantle cell lymphoma as well as other non-Hodgkin lymphomas. This phase II study tested the oral mTOR inhibitor everolimus (RAD001, Novartis Pharmaceuticals) in simultaneous two-stage phase II lymphoma studies, including one arm involving Hodgkin lymphoma. The goals were to learn the toxicity profile and to assess the anti-tumor response. A total of 17 patients with Hodgkin lymphoma were enrolled in the uncommon arm at completion of enrollment. Methods: Patients (pts) received 10 mg PO daily for each 28 day cycle (up to 12, with a possible extension in responders) and restaged after 2, 6, and 12 cycles. The primary endpoint is the confirmed response rate, including CR, CRu or PR. Results: The median age of the 17 pts with Hodgkin lymphoma was 37 yrs (range: 27–68), with a median of 6 (range, 4–14) prior therapies. Fourteen pts (82.4%) had a prior stem cell transplant (SCT). Pts completed a median of 6 (range, 1–13) cycles of therapy. Fifteen of 17 patients were evaluable for response as of this analysis. The overall response rate was 47% (7/15), all partial responses. Ten patients are continuing on study while 6 have gone off due to disease progression and 1 due to other reasons. Common grade 3 adverse events (AEs) include thrombocytopenia (5 pts), anemia (5 pts) and alkaline phosphatase elevation (1 pts). 1 patient was reported to have grade 4 neutropenia. Conclusions: Oral everolimus has promising activity with acceptable toxicity in Hodgkin lymphoma. These results provide the rationale for additional studies with this novel class of agents and to integrate mTOR inhibitors into salvage treatment regimens for Hodgkin lymphoma.
Polymorphisms in One-Carbon Metabolism Genes and Overall Survival in Diffuse Large B-Cell Lymphoma (DLBCL).
Abstract Background. Intracellular one-carbon transfer reactions are essential for nucleotide synthesis and methylation of biologic compounds including DNA. Previous studies have linked genetic variants in one-carbon metabolism genes with risk of developing NHL, but little is known regarding the impact of these variants on disease outcome. We evaluated the hypothesis that inherited genetic variation in genes involved in one-carbon metabolism is associated with overall survival in DLBCL. Methods. We genotyped 30 single nucleotide polymorphisms (SNPs) from 18 candidate one-carbon metabolism genes in 215 DLBCL patients who participated in a population-based case-control study conducted from 1998–2000 using the SEER (Surveillance, Epidemiology and End Results) cancer registries in the Detroit, Iowa, Los Angeles and Seattle. Stage, B-symptoms, first course of therapy, date of last follow-up and vital status through early 2005 were obtained from cancer registry files. Cox proportional hazards analysis was used to estimate hazard ratios (HR) and corresponding 95% confidence intervals for the association between individual SNPs and overall survival, adjusting for age, demographic and clinical factors. We also used parallel modeling strategies to identify the best summary multi-SNP risk score to predict survival. Results. The median age at diagnosis was 57 years (range, 20–74), and 50 (23%) of the patients died during follow-up, with a median follow-up of 57 months (range, 31–78 months) for surviving patients. After adjusting for demographic and clinical variables, SNPs in SHMT1 (rs1979276; HRCT/TT=2.47, 1.31–4.67), BHMT (rs585800; HRAT/TT=2.02, 1.16–3.54), and TCN1 (rs526934; HRTT=1.86, 1.04–3.33) were the strongest and most robust predictors of survival. A summary score of the number of deleterious genotypes (0–3) from these three genes was strongly associated with survival (p=7.9 x 10−5) after accounting for demographic and clinical variables (HR=2.58 per deleterious genotype, 95% CI 1.75–3.80). A risk score combining the three SNPs with clinical and demographic variables (score of 0 to 5) was even more strongly associated with survival (p=1.4 x 10−13); the Kaplan Meier survival curves are shown in the Figure. In a time-dependent ROC analysis, the combined risk score had a concordance index of 0.75 at 5 years of follow-up (95% CI 0.69–0.81). Conclusion: Host genetic variation in the one-carbon metabolism genes SHMT1, BHMT, and TCN1, individually and particularly in combination, was associated with overall DLBCL survival after accounting for clinical and demographic factors, supporting a role for this pathway in disease progression. Future work should evaluate interactions of genes from this pathway with dietary nutrients and therapeutic agents in DLBCL prognosis. Figure Figure
Lenalidomide Response in Relapsed/Refractory Aggressive Non-Hodgkin’s Lymphoma Is Related to Tumor Burden and Time from Rituximab Treatment.
Abstract Background: Lenalidomide (Revlimid®) has been reported to show activity in non-Hodgkin’s Lymphoma (NHL). However, prognostic factors predicting an individual patient’s response were unavailable. Aim: To investigate prognostic factors for lenalidomide response in patients with relapsed/refractory aggressive NHL. Methods: Patients with relapsed/refractory aggressive NHL with measurable disease ≥2 cm after at least 1 prior treatment regimen were eligible. Patients received 25 mg lenalidomide orally once daily on Days 1-21 every 28 days and continued therapy for 52 weeks as tolerated or until disease progression. Response and progression were evaluated using the IWLRC methodology. Univariate analyses using Fisher’s exact test and multivariate analyses using logistic regression were conducted to investigate associations of prognostic variables with response. Results: Forty-nine patients received lenalidomide oral monotherapy. The median age was 65 (23-86) and 24 were female. Histology was diffuse large B-cell lymphoma (n=26), follicular center lymphoma grade 3 (n=5), mantle cell lymphoma (n=15) and transformed (n=3). Median time from diagnosis was 2.7 (0.4-32) years and median number of prior treatment regimens was 4 (1-8). Forty-five (92%) of the patients had received prior rituximab and 63% were rituximab-refractory. Seventeen patients (35%) exhibited an objective response (2 complete responses, 4 complete responses unconfirmed and 11 partial responses). Response to lenalidomide was the same for patients who were refractory to rituximab (30%) and those who were not (31%). Three of 4 patients who were rituximab naive responded. Multivariate analysis including IPI, ECOG PS, stage, LDH, # of extranodal sites, age, sex, # of prior regimens and time from diagnosis identified only time since last rituximab and tumor burden as correlated with response. Response to lenalidomide was associated with low tumor burden (52% for <50 cm2v 0% for ≥50 cm2, P=0.033, odds ratio=10.9) and longer time from rituximab to lenalidomide treatment (52% for ≥ 230 days v 6% for <230 days, P=0.031, odds ratio=6.6). Rituximab depletes normal host B-cells and the kinetics for their loss and recovery are consistent with the timing of lenalidomide activity following rituximab. This may be a basis for this effect. However other tumor/host biological factors may also play a role. Patients with favorable values for both prognostic factors (N=24) had a 67% response rate [RR] compared to a 4% RR for patients with unfavorable values (N=25; P< 0.001) and a progression free survival (ongoing) of 7.5 months v 1.9 months. Although absolute lymphocyte count was not selected as a prognostic indicator of response in the multivariate setting, a trend was evident in the univariate analysis (42% for > 0.6 × 109/L v 9% for ≤0.6 × 109/L, P=0.071). Conclusion: Tumor burden and host immune competence may determine the response of relapsed/refractory aggressive NHL to lenalidomide monotherapy.
G-CSF Administration Increases Pulmonary Toxicity for Hodgkin’s Disease Patients Treated with Bleomycin-Containing Chemotherapy.
Abstract Background: In Hodgkin’s Disease (HD), G-CSF has been used to maintain maximum dose intensity by avoiding neutropenia and treatment delays. Pre-clinical data and anecdotal reports have shown an association between G-CSF administration and bleomycin pulmonary toxicity (BPT). This complication may cause access morbidity and have a detrimental impact on survival in this otherwise good prognosis population. We embarked on a retrospective analysis to determine if G-CSF increased the incidence of this complication or had an impact on outcomes. Methods: We reviewed all patients managed for HD at Mayo Clinic, Rochester, from January 1986 to February 2003. BPT was defined by the presence of pulmonary symptoms, bilateral interstitial infiltrates, and no evidence for an infectious etiology. Patients who received G-CSF support with one or more of their bleomycin-containing chemotherapy cycles were considered as being treated with G-CSF. Results: A retrospective review identified 141 patients with HD treated with a bleomycin-containing regimen. The mean age of patients at diagnosis was 34 years. Fifty four percent were males. The histology was nodular sclerosing in 85%. The Hasenclever index was 0 in 15%, 1 in 35%, 2 in 24%, 3 in 16%, 4 in 9%, and ≥ 5 in 1%. The G-CSF and non G-CSF groups were balanced for poor prognosis risk factors including Hasenclever index. Frontline chemotherapy included ABVD in 57%, MOPP-ABV(D) in 33%, COPP-ABV in 8%, BEACOPP in 3%, and Stanford V in 2%. Forty one percent of patients received radiation. The 5-year overall survival (OS) and progression free survival (PFS) for all patients were 87% and 79% respectively. G-CSF was administered to 52% (74/141) of patients. BPT occurred in 18% of patients (25/141). A higher rate of BPT was observed in patients receiving G-CSF, 26% (19/74) versus 9% (6/67) in non G-CSF patients (p=0.0141). In this population, G-CSF administration was the only factor associated with an increased risk of BPT. There was no difference between the two groups for BPT associated risk factors including radiation, bleomycin dose, renal insufficiency, smoking history, and underlying lung disease. Additionally these risk factors showed no correlation with the development of BPT. The mortality from BPT was 4.2% (6/141) in all patients and 24% (6/25) in patients who developed the pulmonary syndrome. Of the 6 patients who died acutely, 83% (5/6) received G-CSF. CR rates were equal between the G-CSF and non G-CSF groups at 92% and 94% respectively. Five year OS and PFS were equal between the G-CSF and non G-CSF groups at 82% versus 89% (p=0.473) and 74% versus 84% (p=0.152) respectively. Conclusion: G-CSF administration increases the incidence of pulmonary toxicity in HD patients treated with bleomycin based chemotherapy. The major impact was on treatment related morbidity as 5-year OS and PFS were equal between the G-CSF and non G-CSF groups.
Bleomycin Pulmonary Toxicity Does Impact on Hodgkin’s Disease Outcome.
Abstract Background: Bleomycin-containing chemotherapy regimens have become the mainstay of treatment in Hodgkin’s Disease (HD). The risk of bleomycin pulmonary toxicity (BPT) ranges from 0–46% and mortality rates range from 0–27%. Although there is no excepted standard treatment for BPT, corticosteroid treatment, withholding bleomycin from subsequent chemotherapy, and proceeding with a non-bleomycin containing regimen is the most common approach. We reviewed our experience to better delineate outcome and appropriate treatment in these patients. Methods: We reviewed all patients managed for HD at Mayo Clinic, Rochester, from January 1986 to February 2003. BPT was defined by the presence of pulmonary symptoms, bilateral interstitial infiltrates, and no evidence for an infectious etiology. Results: A retrospective review identified 141 patients with HD treated with a bleomycin-containing regimen. The mean age of patients at diagnosis was 34 years. Fifty four percent were males. The histology was nodular sclerosing in 85%. The Hasenclever index was 0 in 15%, 1 in 35%, 2 in 24%, 3 in 16%, 4 in 9%, and >5 in 1%. Frontline chemotherapy included ABVD in 57%, MOPP-ABV(D) in 33%, COPP-ABV in 8%, BEACOPP in 3%, and Stanford V in 2%. Forty one percent of patients received radiation. The 5-year overall survival (OS) and progression free survival (PFS) for all patients were 87% and 79% respectively. BPT was observed in 18% of patients (25/141). There was a significant decrease in OS, 63% in patients with BPT versus 90% in non-BPT patients at 5 years (p=0.0013). The mortality from BPT was 4.2% (6/141) in all patients and 24% (6/25) in patients who developed the pulmonary syndrome. These 6 patients all died within 9 months of their HD diagnosis from BPT. The Hasenclever index was 3 or less in 5 of these 6 patients. CR rates were equal at 91% and 93% in BPT and non-BPT patients respectively (p=0.299). Twenty two percent (31/141) of patients, either symptomatic or asymptomatic, had bleomycin omitted at any time from their regimen with no difference in OS or PFS, 83% versus 88% (p=0.369) and 82% versus 78% (p=0.853) respectively. The mean bleomycin dose was 84 mg/m2 (range of 20–180 mg/m2). Bleomycin dose had no impact on OS or PFS. In BPT patients subsequent non-bleomycin therapy included AVD 44%, MOPP-AV 31%, or no further chemotherapy 25%. The five-year OS was equal between the AVD and MOPP-AV groups at 91%. However in patients who received no further chemotherapy 5-year OS was 30% (p=0.0001). Conclusion: Bleomycin pulmonary toxicity (BPT) results in a significant decrease in OS survival at 5 years in patients being treated for Hodgkin’s Disease. In patients who do not die acutely from pulmonary toxicity both OS and PFS appear equal despite the omission of bleomycin.
Molecular Profiling of Diffuse Large B-Cell Lymphoma Identifies Robust Subtypes Including One Characterized by Host Inflammatory Response.
Abstract Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with recognized variability in clinical outcome, genetic features, and cells of origin. To date, transcriptional profiling has been used to highlight similarities between DLBCL tumor cells and normal B-cell subtypes and associate genes and pathways with unfavorable outcome. Given the genetic heterogeneity in DLBCL, there are likely to be subsets of tumors with different pathogenetic mechanisms and possible treatment targets. To identify DLBCL subtypes that were sufficiently robust to be captured by multiple methods, we analyzed the profiles of 176 newly diagnosed DLBCLs using three different clustering algorithms (hierarchical clustering (HC), self-organizing maps (SOM), and probabilistic clustering (PC)), the top 5% of genes with the highest reproducibility across duplicate samples and largest variation across patient tumors, and a resampling-based method (consensus clustering) that automatically selects the most stable numbers of clusters with each algorithm. Three discrete subsets of DLBCLs -- “Oxidative Phosphorylation” (OxPhos), “B-cell Receptor/Proliferation” and “Host Response” (HR) -- were identified, characterized using gene set enrichment analysis and confirmed in an independent series of newly diagnosed DLBCLs with available array data. There was an association between cluster membership and examined genetic abnormalities in DLBCL. BCL2 translocations were more common in the OxPhos cluster whereas BCL6 translocations were more frequent in the BCR/proliferation cluster. Translocations of either type were uncommon in the HR cluster. Patients with HR DLBCLs were also significantly younger than those with OxPhos or BCR/proliferation tumors; HR patients also had a significantly higher incidence of splenic and BM involvement. The unique characteristics of HR tumors - fewer known genetic abnormalities and prominent host immune and inflammatory cell transcripts -prompted us to assess host immune cells in study tumors using morphologic and immunohistochemical approaches. HR DLBCLs contained significantly higher numbers of morphologically distinct CD2+/CD3+ tumor-infiltrating lymphocytes and interdigitating S100+/GILT+/CD1a-/CD123- dendritic cells. The HR cluster shared features of histologically defined T-cell/histiocyte-richBCL, including fewer known genetic abnormalities, younger age at presentation and frequent splenic and bone marrow involvement. The current study identifies tumor microenvironment and host inflammatory response as defining features in DLBCL, provides insights into the nature of the host immune response in a major DLBCL subtype and suggests rational treatment targets in newly identified tumor groups.