Primary Mediastinal B Cell Lymphoma Treated with CHOP-Like Chemotherapy with or without Rituximab: 5-Year Results of the Mabthera International Trial Group (MInT) Study

The aim of this subgroup analysis of the MInT study was to evaluate the impact of chemotherapy and rituximab in primary mediastinal B cell lymphoma (PMBCL) in comparison to other diffuse large B-cell lymphoma (DLBCL). Extended follow-up was needed to establish long-term effects.

Eligible for the randomized open-label MInT study were patients aged 18–60 years with DLBCL who had 0–1 risk factors according to age-adjusted International Prognostic Index (aaIPI), stage II-IV disease, or stage I disease with bulk. Patients were randomly assigned to six cycles of CHOP-like regimens with or without rituximab. Consolidating radiotherapy was given to sites of primary bulky disease.

Of 824 patients enrolled, 87 had PMBCL and 627 other types of DLBCL. Rituximab increased the rates of complete remission (unconfirmed) in both PMBCL (from 54% to 80%; p =.015) and DLBCL (from 72% to 87%; p<.001). In PMBCL rituximab virtually eliminated progressive disease (PD) (2.5% vs 24%; p =.006), whereas without rituximab PD was more frequent in PMBCL than in DLBCL (24% vs 10%; p =.023). With a median observation time of 62 months for PMBCL and 73 months for DLBCL, the 5-year event-free survival was improved by rituximab for PMBCL (79.1% vs 47.3%; p =.011) and for DLBCL (76.9% vs 59.7%; p <.001). Furthermore, 5-year progression-free survival was improved by rituximab for PMBCL (89.8% vs 60.1%; p=.006) and DLBCL (81.1% vs. 67.8%; p <.001). Overall survival benefit was similar for DLBCL (92.0% vs 80.9%; p <.001) and PMBCL (90.2% vs 78.3%; p =.234).

Addition of rituximab to 6 cycles of CHOP-like chemotherapy improved long-term outcome for young patients with PMBCL and aaIPI 0–1 and eliminated differences in outcome between PMBCL and DLBCL.

No relevant conflicts of interest to declare.