Real-world data analysis of survival outcomes of patients with primary mediastinal large B- cell lymphoma treated with upfront consolidative radiation therapy following immunochemotherapy

Background Primary mediastinal large B-cell lymphoma (PMBCL) is a rare subtype of diffuse large B-cell lymphoma. PMBCL predominantly affects young adults and survival outcomes are favorable. Radiation therapy (RT) has been included in the primary treatment option for PMBCL, but intensified immunochemotherapy has raised doubts about this strategy. This study aimed to explore the role of consolidative RT in the primary treatment of PMBCL. Methods This single-center study retrospectively analyzed the survival outcomes of 65 newly diagnosed PMBCL patients. All 65 patients received rituximab-containing therapy. Patients in this study were divided into three groups based on their primary treatment: (1) EPOCH-R (etoposide, prednisone, vincristine, cyclophosphamide, doxorubicin, and rituximab) ( n  = 7), (2) R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone) only (R-CHOP group, n  = 31, and (3) R-CHOP with consolidative RT (R-CHOP + RT group, n  = 27). Results The estimated objective response rates and complete remission rates for all patients were 86.2% and 63.1%, respectively. Median 3-year progression-free survival (PFS) and overall survival (OS) rates were 72% and 81%, respectively. All patients in the R-CHOP + RT group achieved an objective response, with a complete remission rates of 59.3%. The R-CHOP + RT group demonstrated better PFS compared to those who did not receive consolidative RT ( p  = 0.028), although there was no significant difference in OS ( p  = 0.102). In particular, consolidative RT conferred a survival benefit to patients with initial bulky disease or those who had an insufficient end-of-treatment response. The predictive value of ¹⁸ F-fluorodeoxyglucose positron-emission tomography-computed tomography (PET-CT) in assessing treatment response in PMBCL was revalidated, showing that patients who achieved a negative end-of-treatment PET-CT had significantly better survival outcomes than those who did not. One-fourth of the patients experienced disease relapse, and only 30% achieved long-term lymphoma control. The immune checkpoint inhibitor exhibited modest efficacy in this study. Conclusions R-CHOP is a useful alternative regimen when intensified chemotherapy is not feasible and consolidative RT should be considered in cases of initial bulky disease and insufficient end-of-treatment response.