10203-ML-6 TIRABRUTINIB FOR PRIMARY CNS LYMPHOMA: A SINGLE INSTITUTE RETROSPECTIVE ANALYSIS

Abstract In 2020, Tirabrutinib (TIR) was approved in Japan as a novel treatment for primary CNS lymphoma (PCNSL). However, the position of TIR in relation to the existing therapy, methotrexate (MTX)-based therapy, is still unclear. We are currently using TIR for patients who have insensitivity to MTX, have short-term recurrence after MTX, or have difficulty receiving MTX, with the principle of readministering MTX-based therapy to patients with recurrent disease. The subjects were ten patients treated with TIR at our institute, 6 with multiple relapses, 3 with inability to MTX, and 1 with difficulty in MTX treatment, and the mean number of relapses was 3.8 when Tirabrutinib was used. The mean number of treatments was 104 days, and 7 patients discontinued treatment due to tumor progression, while 3 patients discontinued due to severe skin problems. The median progression-free survival was 99 days, and only one patient was controlled for more than one year. 4 patients received the best supportive care for recurrence after TIR, and one patient received radiotherapy. The four patients in the MTX-based retreatment group had two progressions and two no progressions at the time of the abstract, with a progression-free survival of 133 days, and two patients had CTCAE grade 4 hematologic toxicities that had not occurred with previous therapy. One patient treated surgically died of postoperative pneumocystis pneumonia. Tirabrutinib showed a high early response rate, but the duration of tumor control tended to be shorter than with MTX-based retreatment. This may be due to its use in our institution after multiple relapses and its aggressive administration in MTX-naive patients. It is also important to note that chemotherapy after TIR use is associated with increased hematologic toxicity.