Rituximab induction therapy, survival benefits, and the increasing selection of radiotherapy as the postinduction treatment in patients with primary mediastinal large B-cell lymphoma

Background: Primary mediastinal large B-cell lymphoma (PMBCL) is a rare malignancy that has been reported in young individuals, especially young women. Patients with PMBCL commonly receive rituximab induction. This single-institution study was designed to analyze the clinical benefits of rituximab induction and its impact on postinduction treatments (PITs), especially radiotherapy. Methods: The benefits of rituximab induction were evaluated by complete response (CR), early treatment failure, relapse, and overall survival (OS) rates. The impact of the induction therapy on the adoption of PIT was evaluated by the proportion of patients who had received at the last follow up any PIT modality [i.e., radiotherapy or hematopoietic stem cell transplantation (HSCT)], radiotherapy alone, HSCT alone, or both modalities. Results: Between 1999 and 2012, 48 PMBCL patients (29 men, 60%) were identified; they had a median age of 31 years. Twenty-eight patients received rituximab induction; of these, 23 (82%) patients also underwent fludeoxyglucose-positron emission tomography (FDG-PET) evaluation. Rituximab induction was significantly associated with higher rates of CR and OS, and lower rates of early treatment failure and relapse. Regarding PIT, patients with rituximab induction were more likely to receive radiotherapy alone [with rituximab induction (25%) vs. without rituximab induction (5%)], and patients with FDG-PET evaluation were similarly more likely to receive radiotherapy alone [with FDG-PET evaluation (28.6%) vs. without FDG-PET evaluation (0%)]. In multivariate analysis, age older than 60 years [hazard ratio (HR), 16.697; 95% confidence interval (CI), 1.106-252.022; p = 0.042] and rituximab induction (HR, 0.089; 95% CI, 0.012-0.653; p = 0.017) were significantly associated with OS. Conclusion: Rituximab improved the CR and OS rates of patients with PMBCL, but these improvements may be attributable to the increased use of radiotherapy (which may have also resulted from FDG-PET evaluation).