Tirabrutinib rechallenge achieved complete response for recurrent primary central nervous system lymphoma: illustrative case.

Primary central nervous system lymphoma (PCNSL) is an aggressive non-Hodgkin lymphoma with a poor prognosis, with a 5-year survival rate of 23-42%. Relapse occurs in 35-60% of patients within 1-2 years, and no standard treatment exists for recurrent PCNSL. Tirabrutinib, a second-generation BTK inhibitor, is used for recurrent PCNSL treatment in Japan, but its efficacy in rechallenge therapy remains uncertain. A 75-year-old man presented with gait disturbance, dysarthria, and ataxia. MRI revealed a contrast-enhancing lesion in the right cerebellar hemisphere, and a biopsy confirmed PCNSL. He achieved a complete response with rituximab and high-dose methotrexate, but recurrence occurred a year later in the left frontal lobe. Tirabrutinib induced remission for six months before a new recurrence in the right frontal lobe. After craniotomy with tumor biopsy reconfirmed PCNSL, he underwent rituximab, methotrexate, procarbazine, and vincristine followed by high-dose cytarabine, achieving remission. A third recurrence led to a tirabrutinib rechallenge, and remission lasted five months. He ultimately developed leptomeningeal disease and received best supportive care before passing away three months later. This case highlights the potential of tirabrutinib rechallenge in recurrent case of PCNSL. Further studies are necessary to evaluate its prognostic value in PCNSL management.