QOL-03. Real-world outcomes in older patients with primary CNS lymphoma treated by R-MPV treatment without whole brain radiotherapy

Abstract OBJECTIVE Delayed central nervous system (CNS) complications from whole brain radiation therapy (WBRT) is an important issue for primary central nervous system lymphoma (PCNSL) patients over 60 years old. We evaluated the real-world outcomes of rituximab, methotrexate (MTX), procarbazine, and vincristine (R-MPV) for elderly patients with PCNSL avoiding routine WBRT. METHODS We evaluated ≥60-year-old patients with newly diagnosed PCNSL who received high dose MTX (HD-MTX) based regimen and R-MPV with or without WBRT from January 2008 to January 2024 at Kobe University Hospital. Before July 2016, the treatment strategy was based on HD-MTX followed by WBRT; after August 2016, the treatment strategy was R-MPV therapy avoiding routine WBRT; in case of partial response or less to R-MPV therapy, salvage irradiation was received. The patients’ characteristics, regimen enforcement, response rate, CSF examination, ventricular volume, MRI finding and survival were analyzed. RESULTS Eighty-seven patients were consecutively enrolled. Their median age was 69.5 years old. Thirty one of 40 (78%) patients achieved a complete response (CR) after R-MPV therapy, and all patients achieved a CR after WBRT at 45Gy. Progression-free survival (PFS) was 70.9 months in R-MPV without WBRT and 27.2 months and induction therapy with WBRT treatment (p=0.024). Overall survival rates (OS) were undefined in R-MPV without WBRT and 35.9 months in induction therapy with WBRT (p=0.0081). In addition, higher CSF IL-10 (>100 pg/ml) levels were associated with increased ventricular volume at 1 year (p=0.0234). CONCLUSION In PCNSL patients over 60 years old, R-MPV therapy avoiding WBRT had a better outcome than the induction therapy with WBRT. Moreover, high CSF IL-10 levels were an important factor in the progression of brain atrophy associated with WBRT. Based on the results, we should evaluate appropriate consolidation therapy (reduced-dose WBRT ≤24 Gy or autologous hematopoietic stem cell transplantation) in the future.