Outcome of Primary Mediastinal Large B Cell Lymphoma Treated with RCHOP.

Purpose: Primary mediastinal large B-cell Lymphoma (PMLBCL) is a rare aggressive lymphoma with unique clinical, pathological, and molecular features. The optimal frontline therapy is subject of ongoing debate. Our study aims to evaluate the outcomes of PMLBCL treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (RCHOP) at King Hussein Cancer Center.

Patients and methods: Adult patients >18 years of age with PMLBCL treated with RCHOP from January 2011 to July 2020 were identified. All demographics, disease and treatment related variables were retrospectively collected. Correlations of clinical and laboratory variables with progression-free survival (PFS) and overall survival (OS) were determined by univariate and multivariate analyses using backward stepwise Cox regression models. The PFS and OS were plotted using Kaplan‒Meier curves.

Results: 49 patients were included with a median age of 29 years. 14 (28.6%) had stage III or IV, 31 (63.3%) had mediastinal bulky disease. International prognostic index (IPI) was 0-1 in 35 (71.4%). Radiotherapy was given to 32 (65.3%) patients. End of treatment (EOT) response was complete (CR) in 32 (65.3%), partial response (PR) in 8 (16.3%) and progressive disease (PD) in 9 (18.4%). Patients who achieved CR at EOT, compared favorably with those who did not in regard to 4-year OS (92.5% vs 26.9%, p=<0.001). Overall objective response to salvage chemotherapies was 26.7%. At a median follow-up of 46 months, 4-year PFS and OS were 60% and 71% respectively. In multivariate analysis, IPI > one correlated with the EOT response (p=0.009), PFS (p=0.004) and OS (p= 0.019).

Conclusion: In PMLBCL, RCHOP chemotherapy backbone in the frontline therapy is suboptimal but can be used in patients with low IPI. Adapting more intensive chemoimmunotherapy regimens may be considered for patients with high IPI. Salvage chemotherapy has limited activity in patients with relapsed or refractory disease.