Primary mediastinal B-cell lymphoma: treatment and therapeutic targets

Malignant hematopoietic cell lines: in vitro models for the study of primary mediastinal B-cell lymphomas

Primary mediastinal B-cell lymphoma (PMBL) is a highly aggressive disease with a unique set of biological, clinical, morphological, immunological and in particular genetic features that in the molecular era of defining lymphomas clearly distinguishes it as a separate entity from other diffuse large B-cell lymphomas (DLBCL). A precise molecular diagnosis of PMBL can be achieved by gene expression profiling. The signature gene expression profile of PMBL is more closely related to classic Hodgkin lymphoma (cHL) than to other DLBCL subgroups. A number of common genetic aberrations in PMBL and cHL further underscore their close relationship. To investigate the pathobiology of lymphomas in depth, many groups have turned to cell lines that are suitable models facilitating molecular studies and providing unique insights. For the purposes of the current perspective, we focus on four bona fide PMBL-derived cell lines (FARAGE, KARPAS-1106, MEDB-1, U-2940) that we identified and validated as such through hierarchical cluster analysis among a large collection of leukemia-lymphoma cell lines. These gene expression profiles showed that the four PMBL cell lines represent a distinct entity and are most similar to cHL cell lines, confirming derivation from a related cell type. A validated cell line resource for PMBL should assist those seeking druggable targets in this entity. This review aims to provide a comprehensive overview of the currently available cellular models for the study of PMBL.

Radiation therapy in primary mediastinal B-cell lymphoma with positron emission tomography positivity after rituximab chemotherapy

PURPOSE

To investigate the role of radiation therapy (RT) in patients affected with primary mediastinal B-cell lymphoma (PMBCL) with residual (18)fluorodeoxyglucose positron emission tomography ((18)FDG-PET)-positive disease after rituximab chemotherapy (R-CT).

METHODS AND MATERIALS

Thirty-seven patients treated with R-CT and RT, all with (18)FDG-PET scan at diagnosis and before RT, were included. All (18)FDG-PET scans were reviewed, and responses were classified according to the Deauville 5-point scoring system. Outcomes measures were overall survival (OS) and progression-free survival (PFS), estimated for the whole cohort and for subgroups according to (18)FDG-PET score after R-CT.

RESULTS

The median follow-up time was 40.9 months. Three patients were assigned to Deauville score 1 (8.1%), 9 to score 2 (24.3%), 7 to score 3 (19%), 14 to score 4 (37.8%), and 4 to score 5 (10.8%). After RT, all patients with score 3-4 experienced a complete response (CR). Among patients with score 5, 1 was in CR (25%), 2 had persistent positivity (50%), and 1 showed progressive disease (25%). A total of 4 patients experienced progression or relapse: 1 of 33 (3%) with scores 1-4, and 3 of 4 (75%) with score 5. The 3-year OS and PFS of the whole cohort were 89.8% and 88.7%, respectively. OS was significantly different between scores 1-3 and scores 4-5 (100% vs 77% at 3 years, P<.05). Patients with a score of 5 had a significantly worse outcome than did all other patients (OS at 2 years, 33.3% vs 100%).

CONCLUSIONS

Approximately 50% of PMBCL patients show residual disease at (18)FDG-PET scan after R-CT. RT is able to convert to CR approximately 85% of these patients, but those with a Deauville score of 5 (10%) appear at high risk of progression and death, and they might be candidates for intensified programs.

Outcome and pathologic classification of children and adolescents with mediastinal large B-cell lymphoma treated with FAB/LMB96 mature B-NHL therapy

Mediastinal large B-cell lymphoma (MLBL) represents 2% of mature B-cell non-Hodgkin lymphoma in patients ≤ 18 years of age. We analyzed data from childhood and adolescent patients with stage III MLBL (n = 42) and non-MLBL DLBCL (n = 69) treated with Group B therapy in the French-American-British/Lymphome Malins de Burkitt (FAB/LMB) 96 study. MLBL patients had a male/female 26/16; median age, 15.7 years (range, 12.5-19.7); and LDH < 2 versus ≥ 2 × the upper limit of normal, 23:19. Six MLBL patients (14%) had < a 20% response to initial COP (cyclophosphamide, vincristine, and prednisone) therapy. Central pathology revealed approximately 50% with classical features of primary MLBL. Five-year event-free survival for the stage III MLBL and non-MLBL DLBCL groups was 66% (95% confidence interval [CI], 49%-78%) and 85% (95% CI, 71%-92%), respectively (P < .001; 14%). The 5-year overall survival in the 42 MLBL patients was 73% (95% CI, 56%-84%). We conclude that MLBL in adolescent patients is associated with significantly inferior event-free survival compared with stage III non-MLBL DLBCL and can be of multiple histologies. Alternate treatment strategies should be investigated in the future taking into account both adult MLBL approaches and more recent biologic findings in adult MLBL.

Randomized clinical trial to assess the efficacy of radiotherapy in primary mediastinal large B-lymphoma

PURPOSE

We developed a controlled clinical trial to assess the efficacy and toxicity of adjuvant-involved field radiotherapy (IFRT) in patients with primary mediastinal B-cell lymphoma that achieved complete response after the patients were treated with cyclophosphamide, doxorubicin, vincristine, prednisone, and rituximab (R-CHOP-14).

METHODS AND MATERIALS

Between January 2001 and June 2004, 124 consecutive patients who were in complete remission after dose dense chemotherapy and rituximab administration (R-CHOP14) were randomly assigned to received IFRT (30 Gy). Sixty-three patients received IFR, and 61 patients did not (control group).

RESULTS

The study aimed to include 182 patients in each arm but was closed prematurely because in a security analysis (June 2004), progression and early relapse were more frequent in patients that did not received IFRT. Patients were followed until March 2009, at which point actuarial curves at 10 years showed that progression free-survival was 72% in patients who received IFR and 20% in the control group (p < 0.001), overall survival was 72% and 31%, respectively (p < 0.001). Acute toxicity was mild and well tolerated.

DISCUSSION

Adjuvant radiotherapy to sites of bulky disease was the only difference to have an improvement in outcome in our patients; the use of rituximab during induction did not improve complete response rates and did affect overall survival; patients who received rituximab but not IFRT had a worse prognosis.

CONCLUSIONS

The use of IFRT in patients with primary mediastinal B-cell lymphoma who achieved complete response remain as the best treatment available, even in patients that received rituximab during induction.

[Standard CHOP immuno-chemotherapy for primary mediastinal lymphomas]

INTRODUCTION

Primary mediastinal lymphoma (PMBCL) is an aggressive diffuse large B-cell lymphoma entity. It is a rare disease with specific clinical symptoms. The tumor is predominantly localized in the mediastinum but grows rapidly and infiltrates the surrounding tissues and organs. Two thirds of the patients are young females. Previous studies showed that third generation treatments are more effective than former standard cyclophosphamide-doxorubicin-vincristine-prednisolone (CHOP) regimens.

AIM

Authors' goal was to assess whether adding the anti-CD20 monoclonal antibody, rituximab to the standard CHOP regimen improves the efficacy of the treatment compared to their previous results with CHOP and third generation chemotherapy regimens.

METHODS

Between October, 2002 and December, 2004 they have started the rituximab-CHOP (R-CHOP) treatment of 20 newly diagnosed, previously untreated PMBCL patients. Results were compared to the data of 24 patients receiving CHOP (n = 9) or procarbazin-prednisolone-doxorubicin-cyclophosphamide-etoposide-cytosin-arabinoside-bleomycin-vincristin-methotrexate (ProMACE-CytaBOM) (n = 15) treatment in the past.

RESULTS

During an average follow-up of 64.6 months, the 5-year overall survival (OS) rate was significantly higher in the R-CHOP group compared to the CHOP treatment (79.4% vs. 33.3%; p = 0.026). However, due to the low number of cases, significant statistical difference could not be demonstrated in the 5-year event-free survival (EFS: 70.0% vs. 33.3%; p>0.05), disease-free survival (DFS: 70.0% vs. 33.3%; p>0.05) and relapse-free survival rate (RFS: 93.0% vs. 100%; p> 0.05), despite of the remarkable numeric difference. When comparing the 5-year survival rates of R-CHOP and ProMACE-CytaBOM treatments, the results were very similar without any significant statistical difference between the two types of treatment (OS: 79.4% vs. 80%; EFS: 70.0% vs. 60.0%; DFS: 70.0% vs. 60.0%; RFS: 93.0% vs. 82.0%; p> 0.05 in all cases). With adding rituximab to CHOP treatment, which was previously considered an insufficient treatment on its own, authors have obtained as good results in treating PMBCL as with third generation regimens. Patients have received the R-CHOP treatments without major side effects and mainly as out-patients.

CONCLUSIONS

Standard R-CHOP treatment could therefore replace the more toxic third generation regimens in PMBCL as well. The data are comparable with those reported in the international literature.

Autologous transplant for primary mediastinal B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is a subtype of lymphoma that shares similarities with diffuse large B-cell lymphoma and with classic Hodgkin's lymphoma. The current study evaluates the use of autologous stem cell transplant (ASCT) as part of initial therapy in a cohort of patients with PMBCL treated between 1985 and 2006. The study demonstrates excellent survival and progression-free survival for patients in complete remission (CR) at ASCT, and for those achieving CR after ASCT. It also shows a benefit to administration of involved-field radiation therapy. However, front-line therapy has evolved considerably since these patients were treated. Dose-dense chemotherapy regimens show excellent results without transplant and the incorporation of rituximab in the treatment may have further improved outcomes. Given these excellent results, ASCT should not currently be used in patients in first CR, but ASCT remains the treatment of choice in relapsed and refractory PMBCL. Similarly, radiotherapy is unnecessary in patients in first CR but is probably useful in patients with residual active mass.