Allogeneic hematopoietic stem cell transplantation following T-cell-directed immunotherapy failure in B-cell lymphoma: a real-world case series and systematic literature review.

T-cell-directed immunotherapies, including chimeric antigen receptor T-cell therapy (CAR-T) and bispecific antibodies (BsAbs), have revolutionized the management of B-cell lymphomas, yet options after treatment failure remain limited. We reviewed four patients who underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) after BsAb or CAR-T exposure, and performed a systematic literature review. Three patients had large B-cell lymphoma, one had follicular lymphoma. Two achieved durable remission, whereas two experienced early relapse or transplant-related mortality. The literature search identified six studies, evaluating allo-HSCT as salvage therapy after CAR-T failure or as consolidation following BsAb response. One-year overall survival exceeded 50% after CAR-T failure, with non-relapse mortality ranging from 20% to 33%. Prior CAR-T exposure did not clearly increase transplant-related toxicity, while allo-HSCT following BsAb therapy warrants vigilant infection monitoring and further prospective evaluation. Allo-HSCT may serve as an effective curative treatment after CAR-T or BsAb therapy, particularly in patients with controlled disease.