Long-term remission following CAR-T therapy in a patient with transformed follicular lymphoma relapse after allogeneic stem cell transplantation.

Follicular lymphoma (FL) may undergo histological transformation (HT) into a more aggressive lymphoma. Although rituximab for B-cell non-Hodgkin lymphomas (B-NHL) has greatly improved the overall survival (OS) of patients with transformed FL (tFL), relapse after anthracycline-based chemoimmunotherapy has a poor prognosis. CD19-targeting chimeric antigen receptor-modified T-cell (CAR-T) therapy is a promising treatment for relapsed or refractory (r/r) large B-cell lymphoma (LBCL), including tFL. However, lymphopenia and reduced T-cell fitness caused by bendamustine exposure for treatment of underlying FL may impair the feasibility and reduce the efficacy of CAR-T therapy. Herein, we report the case of a 44-year-old woman with tFL who relapsed following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and received CAR-T therapy. The patient could not initially undergo CAR-T therapy due to lymphopenia caused by bendamustine exposure, but CAR-T therapy became feasible following allo-HSCT. Although CAR-T therapy using T cells harvested from an allo-HSCT recipient may theoretically cause alloreactivity, the patient did not experience graft versus host disease (GVHD) or serious complications specific to CAR-T therapy, such as cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS), and she has remained in complete response (CR) for >18 months. CAR-T therapy following allo-HSCT for patients with r/r tFL may be a safe and effective treatment option. Allo-HSCT may enhance the efficacy of CAR-T therapy.