The impact of MICB mismatches in unrelated haematopoietic stem cell transplantation.

MICA polymorphisms have been associated with increased incidence of acute GvHD and adverse outcome in allogeneic haematopoietic stem cell transplantation (HSCT). MICB is another expressed member of MHC class I-related chain genes and its impact on HSCT outcome is yet to be fully defined. We typed a large cohort of patients and donors for MICB polymorphisms and investigated the impact of MICB matching on outcome after unrelated HSCT. 69.2% of the patients were 10/10 human leukocyte antigen (HLA) matched and 30.8% were 9/10 HLA matched. MICB typing was performed using a short amplicon-based NGS typing assay on the Illumina MiSeq platform. Differences in proteins were considered as mismatches. MICA polymorphisms were identified as possible confounder and were therefore included as parameter in the multivariate analyses. Due to the strong linkage disequilibrium with the classical HLA-genes, sub-stratification for HLA matching status was necessary, and no effect of MICB mismatches was seen in the 10/10 HLA matched group when compared to the MICB matched cases. However, in the 9/10 HLA matched group, MICB mismatched cases showed significantly worse disease free survival (DFS), GvHD and relapse free survival (GRFS) compared to the MICB matched cases (DFS: HR 1.24, p = 0.011; GRFS: HR 1.26, p = 0.002). MICA mismatches had no impact on any outcome parameter. According to our findings, effects previously attributed to MICA differences may have been confounded by MICB polymorphisms. We show that MICB differences contribute a small but relevant effect in 9/10 HLA-matched transplantations, which in turn highlights the possible usefulness of MICB typing in donor selection among similarly suitable 9/10 matched donors, especially when HLA-B mismatches have to be accepted.

Outcomes of pirtobrutinib for relapsed/refractory mantle cell lymphoma in compassionate use program in Europe.

BACKGROUND: Mantle cell lymphoma (MCL) is a type of B-cell lymphoma that is currently incurable. Pirtobrutinib shows promising response rates in heavily pretreated MCL patients according to the approval study, but the real-world data are scarce. METHODS: In this study, we retrospectively analyzed the efficacy and safety profile of pirtobrutinib in 10 relapsed/refractory MCL patients from compassionate use program (CUP). RESULTS: On average, the patients underwent three lines of systemic therapy prior to pirtobrutinib and were predominantly BTKi exposed (9/10). The best overall response rate (BORR) was 67%. In a median follow-up of 8.6 months, the mean duration of response (DOR), progression-free survival (PFS), and overall survival (OS) were not reached. No new safety signals were documented. CONCLUSIONS: In summary, pirtobrutinib represented a safe and effective treatment option in a small real-world population.

Impact of busulfan versus treosulfan dose intensity in myelofibrosis undergoing hematopoietic cell transplantation.

One key aspect of allogeneic hematopoietic cell transplantation (HCT) is pretransplant conditioning, balancing risk for relapse versus non-relapse mortality. Conditioning regimens with different alkylators at different doses can influence outcome, but data are missing for myelofibrosis, a challenging cohort of patients usually presenting at older age and with comorbidities. We evaluated in a multicenter retrospective study the comparative efficacy and safety of busulfan versus treosulfan in combination with fludarabine for myelofibrosis patients undergoing HCT. This study included 1115 patients (busulfan, n = 902; treosulfan, n = 213) receiving first HCT between 2005 and 2021. Patients were generally balanced for key patient characteristics. Overall survival at 4 years was 62% for the busulfan group versus 58% for the treosulfan group (p = .22). Impact on outcome was dose-dependent. Overall survival was 65% (95% CI, 61%-69%) for reduced intensity busulfan versus 69% (95% CI, 54%-84%) for reduced intensity treosulfan, 53% (95% CI, 44%-63%) for higher intensity busulfan, and 55% (95% CI, 46%-63%) for higher intensity treosulfan. Incidence of relapse was similar across intensity groups. In multivariable analysis, the hazard for death (with reduced intensity busulfan as reference) was 0.88 (95% CI, 0.39-2.01) for reduced intensity treosulfan (p = .77), 1.42 (95% CI, 0.96-2.10) for higher intensity busulfan (0.08), and 1.61 (95% CI, 1.14-2.26) for higher intensity treosulfan (p = .006). In terms of non-relapse mortality, comparison was not significantly different, while the hazard ratio for higher intensity treosulfan was 1.48 (95% CI, 0.98-2.23; p = .06). Here, we showed comparable outcomes and improved survival in myelofibrosis undergoing HCT with reduced intensity busulfan or treosulfan.

Chimeric antigen receptor-T cell therapy shows similar efficacy and toxicity in patients with diffuse large B-cell lymphoma aged 70 and older compared to younger patients: A multicenter cohort study.

CD19-directed chimeric antigen receptor (CAR)-T cell therapy has become a standard treatment for relapsed/refractory diffuse large B-cell lymphoma (r/r DLBCL). While the benefits of CAR-T cell treatment are clear in the general patient population, there remains a relative scarcity of real-world evidence regarding its efficacy and toxicity in patients (pts) aged ≥70 years with DLBCL. We conducted a multicenter retrospective analysis including 172 r/r DLBCL pts with CAR-T cell treatment, axicabtagene ciloleucel or tisagenlecleucel, between 2019 and 2023 at three tertiary centers. Pts were grouped by age at CAR-T infusion (<70 vs. ≥70 years). Subsequently, descriptive and survival analyses, including propensity score matching, were performed to compare outcomes between both age groups. We identified 109 pts aged <70 and 63 pts aged ≥70 years. Overall response rates for both age groups were comparable (77.7% vs. 78.3%; p = 0.63). With a median follow-up of 8.3 months, median progression-free survival was 10.2 months (95% confidence interval [CI]: 6.5-21.8) and 11.1 months (95% CI: 4.9-NR) (p = 0.93) for both cohorts. Median overall survival reached 21.8 months (95% CI: 11.8-NR) and 34.4 months (95% CI: 10.1-NR) (p = 0.97), respectively. No significant differences in the incidence of cytokine release syndrome (p = 0.53) or grade ≥3 neurotoxicity (p = 0.56) were observed. Relapse and nonrelapse mortality were not significantly different between both groups. Our findings provide additional support that CAR-T cell therapy is feasible and effective in patients with r/r DLBCL aged 70 years or older, demonstrating outcomes comparable to those observed in younger patients. CAR-T cell therapy should be not withheld for elderly patients with r/r DLBCL.

Development and Validation of a Prediction Model of Outcome After B-Cell Maturation Antigen-Directed Chimeric Antigen Receptor T-Cell Therapy in Relapsed/Refractory Multiple Myeloma.

PURPOSE: Although chimeric antigen receptor T therapy (CAR-T) cells are an established therapy for relapsed/refractory multiple myeloma (RRMM), there are no established models predicting outcome to identify patients who may benefit the most from CAR-T. PATIENTS AND METHODS: This is an international retrospective observational study including patients with RRMM infused with currently available commercial or academically produced anti-B-cell maturation antigen (BCMA) CAR-T. We describe characteristics and outcomes in Europe (n = 136) and the United States (n = 133). Independent predictors of relapse/progression built a simple prediction model (Myeloma CAR-T Relapse [MyCARe] model) in the training cohort (Europe), which was externally validated (US cohort) and tested within patient- and treatment-specific subgroups. RESULTS: The overall response rate was 87% and comparable between both cohorts, and complete responses were seen in 48% (Europe) and 49% (the United States). The median time to relapse was 5 months, and early relapse <5 months from infusion showed poor survival across cohorts, with the 12-month overall survival of 30% (Europe) and 14% (the United States). The presence of extramedullary disease or plasma cell leukemia, lenalidomide-refractoriness, high-risk cytogenetics, and increased ferritin at the time of lymphodepletion were independent predictors of early relapse or progression. Each factor received one point, forming the three-tiered MyCARe model: scores 0-1 (low risk), scores 2-3 (intermediate risk), and a score of 4 (high risk). The MyCARe model was significantly associated with distinct 5-month incidence of relapse/progression (P < .001): 7% for low-risk, 27% for intermediate-risk, and 53% for high-risk groups. The model was validated in the US cohort and maintained prognostic utility for response, survival, and outcomes across subgroups. CONCLUSION: Outcomes of patients with RRMM after CAR-T are comparable between Europe and the United States. The MyCARe model may facilitate optimal timing of CAR-T cells in patient-specific subgroups.

A genome-wide association study on hematopoietic stem cell transplantation reveals novel genomic loci associated with transplant outcomes.

Introduction: Data on genomic susceptibility for adverse outcomes after hematopoietic stem cell transplantation (HSCT) for recipients are scarce. Methods: We performed a genome wide association study (GWAS) to identify genes associated with survival/mortality, relapse, and severe graft-versus-host disease (sGvHD), fitting proportional hazard and subdistributional models to data of n=1,392 recipients of European ancestry from three centres. Results: The single nucleotide polymorphism (SNP) rs17154454, intronic to the neuronal growth guidant semaphorin 3C gene (SEMA3C), was genome-wide significantly associated with event-free survival (p=7.0x10-8) and sGvHD (p=7.5x10-8). Further associations were detected for SNPs in the Paxillin gene (PXN) with death without prior relapse or sGvHD, as well as for SNPs of the Plasmacytoma Variant Translocation 1 gene (PVT1, a long non-coding RNA gene), the Melanocortin 5 Receptor (MC5R) gene and the WW Domain Containing Oxidoreductase gene (WWOX), all associated with the occurrence of sGvHD. Functional considerations support the observed associations. Discussion: Thus, new genes were identified, potentially influencing the outcome of HSCT.

Diagnostic management of blastic plasmacytoid dendritic cell neoplasm (BPDCN) in close interaction with therapeutic considerations.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN), a rare malignancy derived from plasmacytoid dendritic cells, can mimic both acute leukemia and aggressive T-cell lymphoma. Therapy of this highly aggressive hematological disease should be initiated as soon as possible, especially in light of novel targeted therapies that have become available. However, differential diagnosis of BPDCN remains challenging. This retrospective study aimed to highlight the challenges to timely diagnoses of BPDCN. We documented the diagnostic and clinical features of 43 BPDCN patients diagnosed at five academic hospitals from 2001-2022. The frequency of BPDCN diagnosis compared to AML was 1:197 cases. The median interval from the first documented clinical manifestation to diagnosis of BPDCN was 3 months. Skin (65%) followed by bone marrow (51%) and blood (45%) involvement represented the most common sites. Immunophenotyping revealed CD4 + , CD45 + , CD56 + , CD123 + , HLA-DR + , and TCL-1 + as the most common surface markers. Overall, 86% (e.g. CD33) and 83% (e.g., CD7) showed co-expression of myeloid and T-cell markers, respectively. In the median, we detected five genomic alterations per case including mutational subtypes typically involved in AML: DNA methylation (70%), signal transduction (46%), splicing factors (38%), chromatin modification (32%), transcription factors (32%), and RAS pathway (30%), respectively. The contribution of patients (30%) proceeding to any form of upfront stem cell transplantation (SCT; autologous or allogeneic) was almost equal resulting in beneficial overall survival rates in those undergoing allogeneic SCT (p = 0.0001). BPDCN is a rare and challenging entity sharing various typical characteristics of other hematological diseases. Comprehensive diagnostics should be initiated timely to ensure appropriate treatment strategies.

Allogeneic hematopoietic stem cell transplantation in patients aged 60-79 years in Germany (1998-2018): a registry study.

Incidences of diseases treated with transplantation frequently peak at higher age. The contribution of age to total risk of transplantation has not been estimated amidst an aging society. We compare outcomes of 1,547 patients aged 70-79 years and 9,422 patients aged 60-69 years transplanted 1998-2018 for myeloid, lymphoid and further neoplasia in Germany. To quantify the contribution of population mortality to survival, we derive excess mortality based on a sex-, year- and agematched German population in a multistate model that incorporates relapse and graft-versus-host-disease (GvHD). Overall survival, relapse-free survival (RFS) and GvHD-free-relapse-free survival (GRFS) is inferior in patients aged 70-79 years, compared to patients aged 60-69 years, with 36% (95% Confidence Interval [CI]: 34-39%) versus 43% (41-44%), 32% (30- 35%) versus 36% (35-37%) and 23% (21-26%) versus 27% (26-28%) three years post-transplant (P<0.001). Cumulative incidences of relapse at three years are 27% (25-30%) for patients aged 70-79 versus 29% (29-30%) (60-69 years) (P=0.71), yet the difference in non-relapse mortality (NRM) (40% [38-43%] vs. 35% [34-36%] in patients aged 70-79 vs. 60-69 years) (P<0.001) translates into survival differences. Median OS of patients surviving >1 year relapse-free is 6.7 (median, 95% CI: 4.5-9.4, 70-79 years) versus 9 (8.4-10.1, 60-69 years) years since landmark. Three years after RFS of one year, excess NRM is 14% (95% CI: 12-18%) in patients aged 70-79 versus 12% [11-13%] in patients aged 60-69, while population NRM is 7% (6-7%) versus 3% (3-3%). Mortality for reasons other than relapse, GvHD, or age is as high as 27% (24-29%) and 22% (22-23%) four years after transplantation. In conclusion, survival amongst older patients is adequate after allogeneic stem cell transplantation.

Validation of the transplant conditioning intensity (TCI) index for allogeneic hematopoietic cell transplantation.

The intensity of the conditioning regimen given before allogeneic hematopoietic cell transplantation (allo-HCT) can vary substantially. To confirm the ability of the recently developed transplant conditioning intensity (TCI) score to stratify the preparative regimens of allo-HCT, we used an independent and contemporary patient cohort of 4060 transplant recipients with acute myeloid leukemia meeting inclusion criteria from the discovery study (allo-HCT in first complete remission, matched donor), but who were allografted in a more recent period (2018-2021) and were one decade older (55-75 years, median 63.4 years), we assigned them to a TCI category (low n = 1934, 48%; intermediate n = 1948, 48%, high n = 178, 4%) according to the calculated TCI score ([1-2], [2.5-3.5], [4-6], respectively), and examined the validity of the TCI category in predicting early non-relapse mortality (NRM), 2-year NRM and relapse (REL). In the unadjusted comparison, the TCI index provided a significant risk stratification for d100 and d180 NRM, NRM and REL risk. In the multivariate analysis adjusted for significant variables, there was an independent association of TCI with early NRM, NRM and REL. In summary, we confirm in contemporary treated patients that TCI reflects the conditioning regimen related morbidity and anti-leukemic efficacy satisfactorily and across other established prognostic factors.

Autologous-allogeneic versus autologous tandem stem cell transplantation and maintenance therapy with thalidomide for multiple myeloma patients less than 60 years of age: a prospective phase II study

The role of autologous-allogeneic tandem stem cell transplantation (alloTSCT) followed by maintenance as upfront treatment for multiple myeloma (MM) is controversial. Between 2008 and 2014 a total of 217 MM patients with a median age of 51 years were included by 20 German centers within an open-label, parallel-group, multi-center clinical trial to compare alloTSCT to auto tandem transplantation TSCT (autoTSCT) followed by a 2-year maintenance therapy with thalidomide (100 mg/d) in both arms with respect to relapse/progression-free survival (PFS) and other relevant outcomes. A total of 178 patients underwent second SCT (allo n = 132 and auto n = 46). PFS at 4 years after the second SCT was 47% (CI: 38-55%) for alloTSCT and 35% (CI: 21-49%) for autoTSCT (p = 0.26). This difference increased to 22% at 8 years (p = 0.10). The cumulative incidences of non-relapse mortality (NRM) and of relapse at 4 years were 13% (CI: 8-20%) and 2% (CI: 0.3-2%) (p = 0.044) and 40% (CI: 33-50%) and 63% (CI: 50-79%) for alloTSCT and autoTSCT (p = 0.04), respectively. The difference for relapse/progression increased to 33% (alloTSCT: 44%, autoTSCT: 77%) at a median follow-up of 82 months (p = 0.002). Four-year OS was 66% (CI: 57-73%) for alloTSCT and 66% (CI: 50-78%) for auto TSCT (p = 0.91) and 8-year OS was 52% and 50% (p = 0.87), respectively. AlloTSCT followed by thalidomide maintenance reduced the rate of recurrence or progression during a follow-up period of up to 10 years but failed to improve PFS significantly.

Real-world data suggest effectiveness of the allogeneic mesenchymal stromal cells preparation MSC-FFM in ruxolitinib-refractory acute graft-versus-host disease.

BACKGROUND: Patients with steroid-refractory acute graft-versus-host disease (aGvHD) not tolerating/responding to ruxolitinib (RR-aGvHD) have a dismal prognosis. METHODS: We retrospectively assessed real-world outcomes of RR-aGvHD treated with the random-donor allogeneic MSC preparation MSC-FFM, available via Hospital Exemption in Germany. MSC-FFM is provided as frozen cell dispersion for administration as i.v. infusion immediately after thawing, at a recommended dose of 1-2 million MSCs/kg body weight in 4 once-weekly doses. 156 patients, 33 thereof children, received MSC-FFM; 5% had Grade II, 40% had Grade III, and 54% had Grade IV aGvHD. Median (range) number of prior therapies was 4 (1-10) in adults and 7 (2-11) in children. RESULTS: The safety profile of MSC-FFM was consistent with previous reports for MSC therapies in general and MSC-FFM specifically. The overall response rate at Day 28 was 46% (95% confidence interval [CI] 36-55%) in adults and 64% (45-80%) in children; most responses were durable. Probability of overall survival at 6, 12 and 24 months was 47% (38-56%), 35% (27-44%) and 30% (22-39%) for adults, and 59% (40-74%), 42% (24-58%) and 35% (19-53%) for children, respectively (whole cohort: median OS 5.8 months). CONCLUSION: A recent real-world analysis of outcomes for 64 adult RR-aGvHD patients not treated with MSCs reports survival of 20%, 16% and 10% beyond 6, 12 and 24 months, respectively (median 28 days). Our data thus suggest effectiveness of MSC-FFM in RR-aGvHD.

Clinical Implications and Dynamics of Clonal Hematopoiesis in Anti-CD19 CAR T-cell Treated Patients.

Recent evidence revealed important interactions between clonal hematopoiesis (CH) and cellular therapies established for the treatment of hematologic malignancies. The impact of CH on safety, efficacy, and outcome of chimeric antigen receptor (CAR) T-cell therapy is currently under investigation. We analyzed 110 patients with relapsed/refractory B-cell non-Hodgkin lymphoma (n = 105) or acute lymphoblastic leukemia (ALL) (n = 5), treated with Axicabtagene-Ciloleucel (39%), Tisagenlecleucel (51%), or Brexucabtagene autoleucel (10%). Using error-corrected targeted sequencing, a high CH prevalence of 56.4% (variant allele frequency [VAF] ≥1%) at the time of CAR T-cell infusion was detected. The most frequently mutated gene was PPM1D followed by DNMT3A, TET2, ASXL1, and TP53. Variant allele frequencies were significantly lower in B and T cells compared with monocytes and granulocytes. CH did not increase the risk of CAR T-related toxicities. The incidences of cytokine release syndrome and immune effector-cell-associated neurotoxicity syndrome were similar between CHpos and CHneg patients, regardless of clone size, age, or CAR T product. Prolonged cytopenias were not associated with CH. Best overall response rates (ORRs) were numerically but not significantly higher in CHpos patients (ORR 76.7% versus 62.2%; P = 0.13). Furthermore, CH status did not predict progression-free survival or overall survival. Lastly, sequential analysis showed a modest VAF increase of 1.3% and acquisition of novel mutations within 100 days postinfusion. CH was frequent in large B-cell lymphoma/ALL patients receiving CAR T-cells but did not affect toxicity nor treatment response or outcome.

Organ complications after CD19 CAR T-cell therapy for large B cell lymphoma: a retrospective study from the EBMT transplant complications and lymphoma working party.

We investigated ≥ grade 3 (CTC-AE) organ toxicities for commercial CD19 chimeric antigen receptor T cell (CAR-T cell) products in 492 patients (Axi-Cel; n = 315; Tisa-Cel; n = 177) with Large B-cell Lymphoma in the European Society for Blood and Marrow Transplantation (EBMT) CAR-T registry. The incidence of ≥ grade 3 organ toxicities during the first 100 days after CAR-T was low and the most frequent were: renal (3.0%), cardiac (2.3%), gastro-intestinal (2.3%) and hepatic (1.8%). The majority occurred within three weeks after CAR-T cell therapy. Overall survival was 83.1% [79.8-86.5; 95% CI] at 3 months and 53.5% [49-58.4; 95% CI] at one year after CAR-T. The most frequent cause of death was tumour progression (85.1%). Non-relapse mortality was 3.1% [2.3-4.1; 95% CI] at 3 months and 5.2% [4.1-6.5; 95% CI] at one year after CAR-T. The most frequent causes of non-relapse mortality were cell-therapy-related toxicities including organ toxicities (6.4% of total deaths) and infections (4.4% of total deaths). Our data demonstrates good safety in the European real-world setting.

Long-Term Survivors after Failure of Chimeric Antigen Receptor T Cell Therapy for Large B Cell Lymphoma: A Role for Allogeneic Hematopoietic Cell Transplantation? A German Lymphoma Alliance and German Registry for Stem Cell Transplantation Analysis.

The outcome of patients with large B cell lymphoma (LBCL) who relapse or progress after CD19-directed chimeric antigen receptor T cell therapy (CAR-T) administered as salvage therapy beyond the second treatment line is poor. However, a minority of patients become long-term survivors despite CAR-T failure. The German Lymphoma Alliance (GLA) has proposed a hierarchical management algorithm for CAR-T failure in LBCL, aimed at allogeneic hematopoietic cell transplantation (alloHCT) as definite therapy in eligible patients. The purpose of this study was to investigate characteristics, relapse patterns, and management strategies in long-term survivors after CAR-T failure, with a particular focus on the feasibility and outcome of alloHCT. This was a retrospective analysis of all evaluable patients with a relapse/progression event (REL) observed in a previously reported GLA sample between November 2018 and May 2021. REL occurred in 214 of 356 patients (60%) who underwent CAR-T for LBCL in the previous GLA study. An evaluable dataset was available for 143 of these 214 patients (67%). Twenty-six of 143 patients (18%) survived 12 months or longer from REL, 109 (76%) died within the first year after REL, and 8 (6%) were alive but had not reached the 12-month landmark. Long-term survivors had more favorable pre-CAR-T features, had a longer interval between CAR-T and REL, and had more often received a tumor biopsy after CAR-T failure, whereas the choice of the first salvage regimen had no impact. AlloHCT was feasible in 40 of 53 patients (75%) intended and resulted in a 12-month post-transplantation overall survival of 36% in those patients who underwent transplantation with sensitive or untreated REL. AlloHCT after CAR-T failure in LBCL is feasible and may be an important contributor to long-term survival, although selection bias must be taken into account. Thus, alloHCT should be considered as a reasonable treatment option for eligible patients in this setting. However, because the overall outlook after CAR-T failure remains poor, novel effective therapeutic approaches are needed, either to allow long-term disease control per se or to improve the preconditions for successful alloHCT.

Current incidence, severity, and management of veno-occlusive disease/sinusoidal obstruction syndrome in adult allogeneic HSCT recipients: an EBMT Transplant Complications Working Party study.

The current incidence, diagnostic policy, management, and outcome of VOD/SOS at EBMT centers were studied. All centers that had performed allogeneic HSCTs in adult patients within one defined year were invited to the study. Seventy-one centers participated with a total of 2886 allogeneic transplantations and 93 cases of VOD/SOS in 2018. The cumulative incidence of VOD/SOS at day 21 was 1.8% and at day 100 2.4%. Of 67 cases with detailed data, 52 were classical and 15 (22%) late onset (>day 21). According to the EBMT criteria, 65/67 patients had at least two VOD/SOS risk factors. The severity grades were: mild 0, moderate 3, severe 29, very severe 35. Fifty-four patients were treated with defibrotide. VOD/SOS resolved in 58% of the patients, 3/3 with moderate, 22/28 with severe, and 12/33 with very severe grade (p < 0.001). By day 100, 57% of the patients were alive; 3/3 with moderate, 22/29 with severe, and 13/35 with very severe VOD/SOS (p = 0.002). In conclusion, the incidence of VOD/SOS was low. Severe and very severe grades dominated. Very severe grade predicted poor outcome compared to severe grade further supporting the concept of early diagnosis and treatment to avoid a dismal outcome.

Radiation and Dose-densification of R-CHOP in Primary Mediastinal B-cell Lymphoma: Subgroup Analysis of the UNFOLDER Trial.

UNFOLDER (NCT00278408, EUDRACT 2005-005218-19) is a phase-3 trial in patients with aggressive B-cell lymphoma and intermediate prognosis, including primary mediastinal B-cell lymphoma (PMBCL). In a 2 × 2 factorial design, patients were randomized to 6× R-CHOP-14 or R-CHOP-21 (rituximab, cyclophosphamide, doxorubicin, vincristine, and prediso(lo)ne) and to consolidation radiotherapy to extralymphatic/bulky disease or observation. Response was assessed according to the standardized criteria from 1999, which did not include F-18 fluordesoxyglucose positron emission tomography/computed tomography (FDG-PET) scans. Primary end point was event-free survival (EFS). A subgroup of 131 patients with PMBCLs was included (median age, 34 y; 54% female, 79% elevated lactate dehydrogenase (LDH), 20% LDH >2× upper limit of normal [ULN], and 24% extralymphatic involvement). Eighty-two (R-CHOP-21: 43 and R-CHOP-14: 39) patients were assigned to radiotherapy and 49 (R-CHOP-21: 27, R-CHOP-14: 22) to observation. The 3-year EFS was superior in radiotherapy arm (94% [95% confidence interval (CI), 89-99] versus 78% [95% CI, 66-89]; P = 0.0069), due to a lower rate of partial responses (PRs) (2% versus 10%). PR triggered additional treatment, mostly radiotherapy (n = 5; PR: 4; complete response/unconfirmed complete response: 1). No significant differences were observed in progression-free survival (PFS) (95% [95% CI, 90-100] versus 90% [95% CI, 81-98]; P = 0.25) nor in overall survival (OS) (98% [95% CI, 94-100] versus 96% [95% CI, 90-100]; P = 0.64). Comparing R-CHOP-14 and R-CHOP-21, EFS, PFS, and OS were not different. A prognostic marker for adverse outcome was elevated LDH >2× ULN (EFS: P = 0.016; PFS: P = 0.0049; OS: P = 0.0014). With the limitation of a pre-PET-era trial, the results suggest a benefit of radiotherapy only for patients responding to R-CHOP with PR. PMBCL treated with R-CHOP have a favorable prognosis with a 3-year OS of 97%.