Primary Mediastinal (Thymic) Large B-Cell Lymphoma: Experience in Treating 131 Patients at a National Medical Research Center in Russia

Abstract

Background. Primary mediastinal (thymic) large B-cell lymphoma (PMBCL) is one of the primary extranodal tumors and originates from B-cells of thymic medulla. This disease is characterized by specific immunomorphologic and genetic features which distinguish it from other malignant lymphoproliferative disorders with similar parameters. Standard PMBCL treatment consists of immunochemotherapy and subsequent radiotherapy of residual mediastinal tumor. The advantages of one immunochemotherapy regimens over the other in controlled studies have not been shown. Aim. To study current approaches to chemoradiation in PMBCL patients with an attempt to individualize them focusing on various prognostic factors. Materials & Methods. The data of 131 patients with newly diagnosed PMBCL were analyzed, all of them were treated at NN Blokhin National Medical Cancer Research Center in the period from 2000 to 2017. More than a half were women (58 %), median age was 30 years (range 16-70). At different historical periods PMBCL treatment was performed using different immunochemotherapy regimens: MACOP-B±R in 55 (42 %) patients, R-CHOP in 40 (30.5 %) patients, and R-DA-EPOCH in 36 (27.5 %) patients. Radiotherapy was used to treat 99 out of 131 patients. Results. In general, the treatment of all PMBCL patients (n = 131) appeared to be highly effective. The remission rate was 87 %, 3-year progression-free survival (PFS) and overall survival (OS) was 78 % and 88 %, respectively. With median follow-up of 37 months relapses and progression of the disease were detected in 17 (13 %) out of 131 patients within a period of 13 months after initiation of antitumor treatment. There was not a single case of late relapse. The treatment of relapsed patients was not effective: 12-month OS was not higher than 37 %. Intensive immunochemotherapy regimens ACOP±R, R-DA-EPOCH) do not differ in their effectiveness, but they have significant advantages over the standard R-CHOP regimen. The results of positron emission tomography (PET) considered to be an important prognostic factor in PMBCL treatment: 3-year PFS in the PET-negative group was 92 % vs. 26 % in the PET-positive group. Conclusion. The optimal algorithm of PMBCL treatment was elaborated with consideration of clinical factors, immunochemotherapy programs, degrees of tumor regression, its metabolic activity, and radiotherapy method and irradiation area.