[Different initial responses following epcoritamab therapy for relapsed diffuse large B-cell lymphoma with multiple subcutaneous tumors].

A 73-year-old man with diffuse large B-cell lymphoma relapsed for the fourth time in April 2024 after receiving CAR-T therapy for third relapse in July 2023. Following one cycle of DeVIC therapy for tumor debulking, treatment with the bispecific antibody epcoritamab was initiated in May 2024. The lesion in the right cheek rapidly shrank, but the lesion in the left lower leg grew by day 3 of treatment. Without additional interventions, the left leg lesion shrank by day 14. After one cycle of epcoritamab, a CT scan showed a partial response in both lesions. Although histological confirmation was not obtained, the clinical course suggested that the left leg lesion represented pseudo-progression rather than true disease progression. This case indicates that pseudo-progression occurs during the early stages of treatment with bispecific antibodies, as is also observed in CAR-T therapy. Careful assessment is essential to avoid misinterpreting pseudo-progression as treatment failure and prematurely discontinuing effective therapy.