10215-ML-7 CLINICAL OUTCOME OF TIRABRUTINIB IN PCNSL REFRACTORY TO R-MPV THERAPY

Abstract In recent years, R-MPV therapy has been widely used for treatment of primary central nervous system lymphoma (PCNSL). Although a high response rate and favorable prognosis have been reported with R-MPV therapy using multiple drugs, the treatment strategy for cases refractory to induction therapy has not been established. High-dose radiotherapy is currently recommended for refractory cases, however, the efficacy and frequency of adverse events such as leukoencephalopathy are not yet clear. Tirabrutinib has been available for recurrent or refractory PCNSL cases since 2020. However, there have been few reports on the results of tilabrutinib in these refractory cases. We have been using tirabrutinib for these refractory cases since its introduction. Here, we compared the results of tirabrutinib with those before the introduction of tirabrutinib. We investigated 30 cases with PCNSL treated with R-MPV at our hospital since 2013. 5 (16.7%) of the 30 cases revealed refractory to R-MPV. Two cases were promptly treated with irradiation (total 40-45 Gy) and both remitted, but one (a 70's male) had extensive white matter changes. One case (40's female) also had white matter changes but maintained CR for 4 years and 8 months. All three patients treated with tirabrutinib achieved CR or PR immediately, and two patients (a 60's woman and a 70's man) received whole brain irradiation of 23.4 Gy at 26 and 28 days after tirabrutinib introduction and remained in remission for 2 years 3 months and 2 years 4 months respectively with no significant white matter changes. The results suggest that tirabrutinib may be useful for cases refractory to R-MPV therapy. Because the long-term results of tirabrutinib are not yet clear, careful consideration should be given to the necessity of radiotherapy for cases who have achieved remission with tirabrutinib.