CNSC-37. THE ASSOCIATION BETWEEN THE NUMBER OF HIGH-DOSE METHOTREXATE CYCLES AND LONGER REMISSION PERIODS IN PATIENTS WITH PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA: A RETROSPECTIVE REVIEW

Abstract

Abstract Representing 3-4% of newly diagnosed central nervous system tumors, primary central nervous system lymphomas (PCNSL) are rare, extra-nodal non-Hodgkin lymphomas with an overall survival (OS) of 91.9 months. Though patients can achieve a complete response (CR) after first-line therapy, PCNSL typically recurs within two years. Standard treatment involves high-dose methotrexate (HD-MTX)-based polychemotherapy, but the ideal number of HD-MTX cycles that achieves and maintains a CR is unclear. To address this question, we conducted a retrospective review of PCNSL patients. The primary outcome was median OS. Secondary outcomes included the OS of recurrent PCNSL patients (rOS), number of HD-MTX cycles before the first recurrence or CR, and adverse events (AE). Survival analysis was performed using the Kaplan-Meier estimate. Forty-one patients (23 males; median age: 66) were identified. The median OS is 114 months (95% CI 44.9, NA). Twenty-nine patients achieved CR after first-line therapy with a median of five cycles. Eleven patients experienced PCNSL recurrence (rPCNSL), with five patients previously achieving a CR. The median rOS before the first recurrence was 60.4 months (95% CI 6.3, NA). The median number of cycles of HD-MTX before recurrence was three cycles, and the cumulative total of HD-MTX was five cycles. Among the 24 patients without recurrence and with CR, the median OS was not reached, but the median number of HD-MTX cycles before CR was six cycles and cumulatively was six cycles. Complete results of AEs will be updated at the meeting, but they currently include grade III hypokalemia (45.8%), grade III anemia (45.8%), and grade III acute kidney injury (25.0%). Despite the limitations of a retrospective review, our findings suggest that a higher number of HD-MTX cycles is associated with prolonged duration of remission. Future studies are warranted to determine an ideal number of HD-MTX to maintain remission state in PCNSL patients.