Case series of long-term responders to pralatrexate in peripheral T-cell lymphoma

Peripheral T-cell lymphoma (PTCL) is a heterogeneous group of diseases with a tendency to relapse and poor prognosis, especially in relapsed or refractory cases. The prognosis of patients who are not eligible for autologous hematopoietic stem cell transplantation, such as older adults and those who do not respond to chemotherapy, is extremely poor. In the phase I/II study of pralatrexate in Japanese patients with relapsed or refractory PTCL, the objective response rate was 45%, the median PFS was 150 days, and long-term remission or disease maintenance was possible in approximately 20% of the patients. However, the characteristics of patients who respond to pralatrexate are unknown. Against this background, we investigated common patient characteristics in patients who achieved long-term responses to pralatrexate. Five patients were included and their characteristics were evaluated. The disease types were PTCL-not otherwise specified (NOS) in four cases and angioimmunoblastic T-cell lymphoma (AITL) in one case. The median duration of treatment with pralatrexate was 18 months (range: 7-36 months), of which 3 patients are still being treated. There were no pathological or immunohistochemical findings common to cases that responded to pralatrexate, however, of the four PTCL-NOS patients, two were GATA3 positive. Although there are limitations due to the number of cases, considering that the response rate of pralatrexate for PTCL-NOS in existing studies was 32%, these results may lead to future advances in PTCL treatment.