Real world experience of R-CHOP with or without consolidative radiotherapy vs DA-EPOCH-R in the first-line treatment of primary mediastinal B-cell lymphoma

Primary mediastinal large B-cell lymphoma (PMBCL) is a distinct clinico-pathological subtype of diffuse large B-cell lymphoma with unclear prognostic factors and limited clinical data. Optimal treatment and role for radiotherapy is not fully defined. We performed a multicenter retrospective review of 124 patients with newly diagnosed PMBCL between 2001 and 2016. Treatment regimens were R-CHOP (n = 41), R-CHOP + RT (n = 37), and DA-EPOCH-R (n = 46). 6% (n = 3) in the DA-EPOCH-R group received RT. With a median follow up of 45 months, the overall 5-year OS and PFS was 89.4% and 82.4%, respectively. The type of chemo-radiotherapy regimen, B symptoms and Ann-Arbor staging showed a significant association with OS on univariate analysis but only B symptoms remained prognostic (P = 0.012) after multivariate analysis. The chemo-radiotherapy regimen, Japanese IPI and Ann-Arbor stage was significantly associated with PFS in univariate analysis, but only chemo-radiotherapy regimen remained significant (P = 0.02) after multivariate analysis. Patients who received R-CHOP + RT or DA-EPOCH-R had better PFS than those receiving R-CHOP alone, with 5-year PFS of 90% vs 88.5% vs 56%, respectively (P = 0.02). In the subgroup analysis of patients with bulk (n = 71), R-CHOP alone (n = 21) had inferior 5-year PFS 56.6% compared to those who received R-CHOP + RT (n = 23) 91.3% or DA-EPOCH-R (n = 27) 92.6% (P = 0.007). In contrast, in patients without bulk (n = 42), there was no impact of treatment regimen on PFS (P = 0.25). In conclusion, R-CHOP + RT and DA-EPOCH-R provide excellent outcomes in patients with PMBCL. In patients with bulky disease, the use of DA-EPOCH-R may be preferable as it allows omission of RT without reduction in efficacy.