P11.16.A Questioning convention - is intrathecal chemotherapy (ITC) necessary for patients with newly diagnosed primary central nervous system lymphoma (PCNSL): combined results from three independent cohorts

Abstract Background Despite beguiling responses to initial therapy in many patients, PCNSL remains a therapeutic challenge. Relapse is common, cures are elusive for most and overall response disappointing compared other diffuse large B-cell lymphomas. High-dose methotrexate-based therapies have become the standard of care, with variations, but there no consensus, very little data regarding role ITC treatment patients PCNSL. Material Methods We collected study-level where possible, patient-level from three independent clinical trials comparing adults newly diagnosed treated regimens that differed based on use ITC. Patient characteristics, (OS) progression-free survival (PFS), characteristics relapse were examined. The frequency lymphomatous meningitis at diagnosis location CSF sampling - ventricular vs. lumbar was also investigated. Complete retrieval this updated analysis has allowed us combine studies calculate summary statistics using random effects model inverse variance technique. In addition, predictors OS PFS modeled Cox proportional hazards Results cohorts with: HD MTX/rituximab/ifosfamide followed by either MTX/cytarabine/ifosfamide (group Ia), or cytarabine/thiotepa autologous stem cell transplant Ib) (n=80); HDMTX/vinca alkaloids/ifosfamide/cytarabine II) (n=83); MTX/rituximab III) (n=49). consisted MTX/cytarabine/prednisolone Ia only, n=43); II, n=65); liposomal cytarabine III, n=21). One- two-year better chemotherapy no-ITC group (RR 1.25 [1.16-1.34] 1.20 [1.14-1.26] respectively, p< 0.001 both comparisons). One-year improved 1.12 [1.01-1.25], p=0.031). Two-year not statistically different between groups [0.90-1.59], p=0.220). involving more frequent non-IT 2.31 [2.03-2.62], 0.001). cytology positive 81% specimens vs 14.3% (p< Conclusion This suggests (when rather than sampled) dramatically frequent, perhaps universal. Including as part regimen increased substantially. A randomized controlled trial urgently required.