Review of Primary Mediastinal Large B Cell Lymphomas in Our Hospital
Authors: Hurst Kati , Moragues Martinez Maria Cristina , Espeso de Haro Manuel , Barrios Garcia Manuel , Heiniger Mazo Ana Isabel 
Published: October 2019

Abstract
BACKGROUND: Primary mediastinal B-cell lymphoma (PMBCL) are a subtype of diffuse large B cell lymphoma (DLBCL), that represent 2-4% of all non-Hodgkin lymphoma (NHL) and 6-12% of DLBCL. They affect young adults with a median age at diagnosis of 35 years old and are more frequent in females (2:1). Approximately 80% of patients have stage I or II disease at the time of diagnosis, with B symptoms, bulky mass and superior vena cava syndrome (SVCS) in 50 %. There is no standard initial therapy regimen, anthracyclines with Rituximab are the most used. Local consolidation radiotherapy (RT) is reserved for bulky disease and to complete partial remissions (PR) after chemotherapy.
AIMS: To analyze prognostic and epidemiological factors, treatment administered and response and survival rates of patients diagnosed with PMBCL in our center.
METHODS: Retrospective cohort study between September 2003 and June 2014. The treatment received was 6 to 8 cycles of CHOP-like chemotherapy (Cyclophosphamide, Adriamycin, Vincristine, Prednisone ± methotrexate / Intrathecal triple therapy MTX- TIT ), with or without Rituximab, and subsequent radiotherapy if necessary. The following results were evaluated by univariate analysis: overall survival (OS), disease-free survival (DFS) and incidence of relapse after diagnosis. DFS was defined as the interval of time from complete remission (CR) to relapse or last visit. Response to treatment was assessed by PET-CT.
RESULTS: We observed 14 patients diagnosed with PMBCL in our hospital with a median age of 33 years (r, 21-58 years) and female predominance (Š:‰ 10:4). At diagnosis 42.8 % had B symptoms and 42.8% elevated lactic dehydrogenase. Fifty percent of patients presented with SVCS. Central nervous system and bone marrow infiltration was not observed. Early-stage disease at diagnosis (I 30% and II 53%) was observed in 83%, with IPI 1 in 78.5% of patients. The number of cycles received was 6 in 78.5 %, 8 cycles in 14.2 %, and only 1 cycle of CHOP in one patient. Altogether 71.4 % received Rituximab and 71.4 % received MTX-TIT. Ten patients (71.4%) received RT (median 36 Gy) after chemotherapy, 9 of which had initial bulky disease. We observed an overall response rate of 92.8 % after chemotherapy (57.1 % CR, 35.7% PR). After a median follow-up of 60 months (r, 4.4 to 130.8 months) 12 patients had responded to treatment, were alive, without relapse and in complete response, and one patient is currently receiving the 6º cycle of CHOP pending reevaluation (awaiting last MTX-TIT and RT consolidation) and obtained CR after the third cycle of R-CHOP-MTX-TIT. Median overall survival was not reached and median DFS was of 54.8 months. Only one patient died (mortality 7.1 %) due to influenza A in the context of postchemotherapy aplasia after the first cycle of CHOP.
CONCLUSIONS: We observed prognostic and epidemiological factors similar to those described in literature, although in our series, CHOP -like chemotherapy ( ± MTX- TIT ) with or without Rituximab and RT has shown improved survival rates and 100% of CR. Consolidation radiotherapy was successfully used to complete treatment in patients that only achieved PR after chemotherapy. Rescue chemotherapy followed by autologous hematopoietic cell transplantation was not required. It is difficult to draw conclusions on the impact of the therapeutic regimen received, we believe multicenter analysis with larger numbers of patients are necessary.

Disclosures
No relevant conflicts of interest to declare.