P27.29.A USE OF FOCAL- COMPARED TO WHOLE BRAIN-RADIOTHERAPY IS ASSOCIATED WITH IMPROVED OVERALL SURVIVAL IN PATIENTS WITH PRIMARY CNS LYMPHOMA - RESULTS OF A LARGE MULTI-CENTRIC ANALYSIS FROM THE NEURO-RADIO-ONCOLOGY WORKING GROUP OF THE GERMAN ASSOCIATION OF RADIATION ONCOLOGY (DEGRO AG NRO)
Authors: S Heider, A Rühle, L Allwohn, F Ehret, D Kaul, M Oertel, N Pepper, R Bodensohn, A M Ruder, R Merten, S Combs, D Bernhardt, F Schneller, N Hartong, A L Grosu, N H Nicolay, C Seidel
Journal: Neuro-Oncology (2024)

Abstract BACKGROUND Primary CNS lymphoma (PCNSL) is a rare but deadly disease. Treatment primarily comprises high-dose chemotherapy involving methotrexate. Regarding the use of radiotherapy (RT) as consolidation or primary treatment, or in the setting of recurrent disease, comprehensive multicentric data are sparse. Particularly, comparative data concerning different RT concepts like focal- (FRT) or whole brain radiotherapy (WBRT) are missing. MATERIAL AND METHODS Within a multi-center registry of the German Society for Radiation Oncology − Working Group Neuro-Radio-Oncology (DEGRO AG-NRO), patients that were treated between 2007-2023 for PCNSL and received RT at any time during their disease were included. Among these, a comparative survival analysis was performed on patients who were treated with FRT compared to those who were treated with WBRT. RESULTS 153 patients from 8 German large tertiary centres were included. The median age at the time of diagnosis was 66.5 years (range: 27-89 years), median ECOG was 2 (range: 0-4). 18% (n=27) of patients received primary RT, 33% (n=49) consolidation treatment after initial chemotherapy and 49% (n=79) were treated with RT at recurrent disease. WBRT was most frequently used (primary/consolidating treatment: n=76, 77.6%; recurrent disease: n=62, 83.3%), FRT was less frequently applied (primary/consolidating treatment: n=17, 22.3%; recurrent disease: n=11, 14.9%). Median overall survival (OS) in the entire cohort was 24.1 months (95% CI 14.7-33.4 months), and median survival from the start of radiotherapy was 7.2 months (95% CI 4.5-10.00 months). In patients treated with FRT, the median OS was 67.6 months (95% CI 35.7-99.6 months) compared to patients with WBRT (median OS: 20.1 months, 95% CI 10.5-29.8 months; p=0.016). Likewise, survival from the start of RT was longer after FRT (median: 44.0 months, 95% CI 5.9-82.1 months) than with WBRT (median: 5.8 months, 95% CI 3.2-8.4 months); p=0.017. Differences in survival from RT were discernible in the setting of recurrent disease (FRT: median 8.2 months, 95% CI 0.0-30 months; WBRT: median 3.6 months, 95% CI 1.5-5.6 months; p=0.045) and in primary treatments (FRT: median 44.0 months, 95% CI 0.0-97.2 months; WBRT: median 11.5 months, 95% CI 0.0-33.9 months; p=0.19). In the Cox multiple regression analysis, non-DLBCL histology (HR=0.345; 95% CI, 0.162-0.733; p&amp;lt;0.01) and FRT (HR=0.518; 95%CI, 0.270-0.993; p&amp;lt;0.05) were associated with an improved OS. Size of target volume appeared not associated with OS (Cox regression, p=0.43). CONCLUSION RT for treating PCNSL is mainly used in elderly and frail patients. Treatment concepts are heterogeneous. The use of FRT compared to WBRT during the course of the disease appeared associated with longer survival.