P17.10.B RETROSPECTIVE ANALYSIS OF RADIOCHEMOTHERAPY WITH CONCURRENT OR SEQUENTIAL TUMOR-TREATING FIELDS (TTFIELDS) IN PATIENTS WITH HIGH-GRADE GLIOMA (HGG) IN CHINA.

Abstract BACKGROUND High-grade gliomas (HGG) are aggressive primary Central Nervous System(CNS)tumors with poor survival outcomes and limited treatment options. Tumor-treating fields (TTFields) therapy, using low-intensity electric fields, has shown promise when combined with radiochemotherapy (CRT). The EF-14 trial demonstrated survival benefits of TTFields with temozolomide after radiotherapy in glioblastoma patients, improving both progression-free survival (PFS) and overall survival (OS). This study compares survival outcomes and failure patterns in HGG patients receiving TTFields concurrently with or sequentially after CRT. MATERIAL AND METHODS This study included 114 HGG patients: 70 received concurrent TTFields with CRT (CC-TTF), and 44 received sequential TTFields after CRT (S-TTF). Statistical analysis was performed using R 4.1.0, with Chi-square tests for group comparisons and Cox regression models for OS and PFS. Kaplan-Meier survival curves and log-rank tests assessed survival differences. RESULTS As of February 20, 2025, patients in the S-TTF group had significantly longer median PFS compared to those in the CC-TTF group (17.9 months vs. 13.2 months; p = 0.0175). Although the S-TTF group showed a favorable trend in OS, it was not statistically significant (33.4 months vs. 21.6 months; p = 0.1355). Among recurrent IDH-wildtype gliomas, the S-TTF group had superior median PFS (12.62 months vs. 8.44 months; p = 0.0363) and a trend toward improved OS (23.7 months vs. 18.0 months; p = 0.0666). Recurrence rates were 57% in the CC-TTF group, with 26% distant metastasis and 23% local recurrence. In the S-TTF group, recurrence was lower (48%), with distant progression as the predominant pattern (34%). The higher distant progression rate in the S-TTF group may be linked to TERT wild-type status (p = 0.0516) and delayed TTFields initiation(≥2.22 months after diagnosis, AUC = 0.691, 95% CI: 0.557-0.824, p = 0.0388). CONCLUSION The S-TTF group showed better survival outcomes than the CC-TTF group, with altered recurrence patterns. The higher incidence of distant progression in the S-TTF group may be due to TERT wild-type status and delayed TTFields therapy initiation.