Primary Mediastinal B-cell Lymphoma (PMBCL) is an uncommon entity, comprising less than 4% of non-Hodgkin lymphomas. R-CHOP plus radiotherapy (RT) has been the standard upfront regimen but DA-EPOCH-R has enabled better results with the preclusion of RT, whilst there are no prospective comparative studies. Features and treatment outcomes of PMBCL in low/middle incomes countries are still largely unknown. In this retrospective, single-center, chart-review study, we aimed to ascertain the characteristics of our patients with this disease and the outcomes between R-CHOP/R-CHOEP and DA-EPOCH-R, in a resource-constrained real-life scenario.

Patients with PMBCL diagnosed between 2008 - 2018 treated with rituximab-based first-line therapy were eligible. Treatment response was based on the original radiology reports (CT or PET-CT, according to Cheson and Lugano criteria, respectively).

A total of 95 patients were included. Median age was 28 years (15 – 74 years) and 59.1% were female. Stages I-II performed 57.1% and 31.9% had extranodal disease. Bulky disease was detected in 92.1%, performance status 0-2 in 91.2% and thromboembolic events in 37% of patients. DA-EPOCH-R (41.9%), R-CHOP (35.5%), R-CHOEP (19.3%) and a ‘reduced'R-CHOEP (3.2%) comprised the upfront regimen. Cytoreductive chemotherapy was administered in 50%. Age, staging and presence of bulky disease were similar in the three main regimens. Overall interim assessment (after four cycles) ensured complete response (CR), partial response (PR) and progressive disease (PD) rates of 40%, 55.7% and 4.5%, respectively. At the end of treatment, metabolic CR and rate was 56.8% while 11.1% experienced progression. Mediastinal RT was performed in 42.1% of DA-EPOCH-R, 75% of R-CHOP and 83% of R-CHOEP groups (p = 0.002) and switched PR to CR in 73.7% of them. Estimated 5-year PFS and OS were 77.2% and 77.4%, respectively, and there was no statistical association between treatment and OS, PFS or relapse treatment. In a multivariable analysis, only LDH levels remained independently associated with PFS (HR = 3.1, p = 0.02).

Our cohort showed similar features described in other papers and although near one-third of our patients received R-CHOP as a frontline treatment, a gradual replacement by DA-EPOCH-R could be observed. In many cases, however, we were forced to shift back to a R-CHOEP regimen, due to unavailability of hospital beds. Albeit DA-EPOCH-R showed remarkable results on its original reports, our experience suggests it might not be better than R-CHOP/CHOEP, and allowing yet, the omission of RT. Despite our excessive referral to RT, which could be associated to residual mediastinal uptake at final PET-CT, RT showed to be profitable for partial responders.

Albeit the limited number of patients and the retrospective aspect of this chart-review study, we found no difference in outcomes between a more intensified inpatient and conventional outpatient treatment regimens. Hence, in a resource-constrained scenario, such as Brazil, where a 4-day inpatient chemotherapy infusion could be logistically problematic, R-CHOP or R-CHOEP plus radiotherapy may be still safely adopted. Further studies on economic costs of each approach are still needed.