P14.84 Intraarterial chemotherapy and osmotic blood-brain barrier modification in the treatment of primary CNS lymphoma

BACKGROUND Primary central nervous system lymphomas (PCNSL) are considered a rare and aggressive form of central nervous system (CNS) tumors. High-dose methotrexate has become the backbone of PCNSL treatment, and is recommended by the EANO guidelines. In most recent protocols, investigators tend to postpone or even avoid the use of radiotherapy; indeed, its use has become controversial with findings of associated severe neuro-toxicity, especially in elderly patients. To maximize delivery across the BBB, we use cerebral intra-arterial chemotherapy (CIAC) coupled with osmotic blood-brain barrier disruption (OBBBD). We hereby report our single-center experience over 18 years with the CIAC + BBBD technique using 2 different HD-MTX protocols. MATERIAL AND METHODS This phase II study was conducted at the Centre hospitalier Universitaire de Sherbrooke (CHUS) from November 1999 to May 2018. The protocol was approved by the institutional review board, and informed consent was obtained in accordance to institutional regulation in every patient After enrollment and initial evaluation, patients were treated every four weeks (1 cycle) for 12 cycles, unless progression. After general anesthesia, a transfemoral approach was used to catheterize either the right or left internal carotid artery or the dominant vertebral artery, depending on tumor(s) location. OBBBD was performed by infusing 20% mannitol in the selected vascular distribution for 30 seconds at a rate that fills the vascular distribution so as to maximize the contact of the mannitol with the endothelial cells.Two different chemotherapy regimens were sequentially used in this study. High-dose MTX (5 g IV) was the cornerstone of both regimens: the first regimen (1999 to 2007) also included etoposide phosphate IV (400 mg/m²) and cyclophosphamide IV (660 mg/m²), whereas the 2nd regimen (1998 to 2018) also included carboplatin IA (400 mg/m²). RESULTS The present analysis therefore concerns a cohort of 44 naive patients recruited over 18 years in a single center. Median follow-up was 38 months. Overall, a CR was induced in 34 patients (79%). Themedian time to CR was 7.3 months (IQR: 7.8). Of these 34 patients, 11 (25.6%) are still alive, and 9 of these are disease-free after treatment discontinuation. The actuarial median survival (MS) was 46.5 months (95% CI: 30.9–62.2) for the cohort. Survival was 88%, 64%, 54%, 39% and 18% at 1, 2, 3,5 and 10 years (Figure 1 and Table 2).The progression-free survival was 43.4 months (95% CI: 17.9–68.9). Five occurrences of vascular complications related to the treatment were observed (11.6%). Conclusion: CIAC HD-MTX-based protocols with OBBBD is a safe and well-tolerated procedure for the management of primary CNS lymphoma. Our single center data suggests better PFS and survival outcomes compared to IV protocols with less hematologic toxicity and good tolerability, especially in the elderly.