Efficacy and safety of rituximab treatment in patients with progressive transformation of germinal centers after Hodgkin lymphoma in complete remission post-induction chemotherapy and radiotherapy.

Because the lymphatic tissue of progressive transformation of germinal centers (PTGC) expresses CD20, rituximab treatment may prevent transformation to lymphoma of this rather atypical entity. We prospectively evaluated the efficacy of immunotherapy with rituximab (375 mg/m2 i.v. weekly for 4 consecutive weeks, followed by a single i.v. infusion of 375 mg/m2 every 3 months for 2 consecutive years) in 48 patients with biopsy-proven PTGC after Hodgkin lymphoma in complete remission post-induction therapy (4-6 courses of anthracycline-containing chemotherapy with radiotherapy). The event-free survival (EFS) of this series was compared with that of a historical cohort of 48 patients with PTGC developing after Hodgkin lymphoma in complete remission post-induction therapy, who underwent observation. At a median follow-up of 40 months, histology showed a malignancy in 27% of patients in the observation group (Hodgkin lymphoma, 13 patients) and in 2% of patients in the rituximab-protected group (non-Hodgkin lymphoma, one patient) (p ∼ 0.001). Rituximab was well tolerated in all treated patients. All relapses in the group not protected by immunotherapy involved the PTGC regions and non-contiguous nodal sites, which suggests that PTGC is a reservoir for malignant transformation and dissemination. The number needed to treat with rituximab to avoid one Hodgkin lymphoma relapse was four. Our study shows that prophylaxis with rituximab helps improve EFS in patients with PTGC and a history of Hodgkin lymphoma.