[Long-term remission in refractory diffuse large B-cell lymphoma with concurrent epcoritamab and radiotherapy]

Epcoritamab, a subcutaneous CD3×CD20 bispecific antibody, has shown high efficacy in relapsed or refractory large B-cell lymphoma (R/R LBCL). However, treatment options are limited for patients who fail to achieve durable remission after immune-based therapy. Here, we describe a case of refractory diffuse large B-cell lymphoma in an 87-year-old woman who achieved long-term remission through concurrent epcoritamab and radiotherapy. During the fifth cycle of third-line epcoritamab therapy, positron emission tomography/computed tomography revealed persistent fluorodeoxyglucose-avid lesions in the spleen and mediastinum. Volumetric modulated arc therapy of 36 Gy in 18 fractions was administered to both sites while continuing epcoritamab (administered during the sixth cycle for the splenic lesion and during the thirteenth and fourteenth cycles for the mediastinal lesion). The combined therapy resulted in complete metabolic response without significant adverse events, and the patient remains in remission beyond 27 treatment cycles. In this case, we obtained durable remission by adding radiotherapy for localized lymphoma refractory to epcoritamab. The absence of cross-resistance between radiotherapy and systemic chemotherapy supports the rationale for local irradiation as a complementary approach to bispecific antibody therapy. This combination may represent a feasible and well-tolerated option for elderly or heavily pretreated patients with localized refractory disease.