Modern radiation therapy in part of treatment primary mediastinal (thymic) B-large cell lymphoma (results of 131 patients treated at N.N.Blokhin National Medical Research Center of Oncology of the Ministry of Health of the Russian Federation)

Background. For many decades of the twentieth century, radiation therapy has played a leading role in the treatment of patients with lymphoproliferative diseases, which are highly susceptible to ionizing radiation by neoplasms. But due to the effective development of chemotherapy, the discovery and rapid introduction of targeted drugs into practice, the role of radiation treatment in various types of lymphomas becomes less defined in many clinical situations. Primary mediastinal (thymic) B-cell lymphoma (PMBCL) belongs to the primary extranodal tumors and originate from a thymic medullary B cell. The disease has specific morphoimmunological and genetic characteristics that allows it to be identified from the others similar in manifestations lymphoproliferative diseases. The standard of treatment for PMBCL is immunochemotherapy with subsequent irradiation of a residual tumor in the mediastinum. Currently, the benefits of one chemotherapy regimen over the other ones have not been shown in controlled studies. Aim. To study the modern approaches to the chemoradiotherapy in PMBCL patients with an attempt to "individualize" them depending on various prognostic factors. Methods. The study conducted a thorough analysis of the treatment results of 131 patients with PMBCL who were treated in the N.N.Blokhin National Medical Research Center of Oncology from 2005 to 2017. More than half of the patients were women (58%), the median age was 30 years. At different historical periods, the treatment of PMBCL was applied according to different chemotherapy regimens: MACOP-B+R - 55 (42%), R-CHOP - 40 (30.5%), R-DA-EPOCH - 36 (27.5%); 99 patients received radiation therapy. Results. The efficacy of treatment in the whole group of PMBCL patients was high: remission was achieved in 87% of patients, 3-year progression-free survival was 78%, and overall survival was 88%. With a median follow-up of 37 months, 17 (13%) of 131 patients had a relapse or progression of the disease within 13 months from the start of treatment; no late relapses were detected. Treatment of this group was ineffective: the 12-month overall survival did not exceed 37%. In the group of 99 patients with immunochemoradiotherapy, high rates of 3-year overall survival and progression-free survival (with a median of 37 months) were achieved - 91% and 88%, respectively. It has been shown that intensive immunochemotherapy regimens (R-MACOP-B, R-EPOCH) do not differ in efficacy and have statistically significant advantages over the standard R-CHOP regimen. Positron emission tomography (PET) is an important prognostic tool in the treatment of patients with PMBCL: 3-year progression-free survival in the PET-negative group was 92% compared with 26% in the PET-positive group. The frequency of radiation damage to the lungs during conventional and 3D conformal radiation therapy was analyzed. Conclusion. The algorithm of optimal treatment for PMBCL patients was determined based on clinical factors, the drug treatment program, the degree of regression of the tumor and its metabolic activity, volume and method of irradiation.

primary mediastinal B-cell lymphoma, treatment, prognostic factors, radiotherapy