CNSC-21. THE EFFICACY OF TUMOR TREATING FIELDS IN TREATING IDH-MUTANT ASTROCYTOMA, WHO GRADE 4: AN EARLY RESULT FROM SHANGHAI HUASHAN HOSPITAL

Abstract OBJECTIVES There is ongoing debate regarding the efficacy of Tumor Treating Fields (TTFields) for treating IDH-mutant grade 4 astrocytoma (IDHmA4). In fact, the evidence supporting TTFields in treating IDHmA4 is largely extrapolated from EF-14, of which the results stem form heterogeneous entities of glioblastoma lack of IDH status. This study was conducted by reviewing the database in our center following the release of WHO CNS 5, aiming to preliminarily explore the efficacy of TTFields and prognosticators of newly-diagnosed IDHmA4. METHODS This retrospective analysis included 53 consecutive patients with newly-diagnosed IDHmA4, who underwent radiotherapy at Huashan Hospital, Fudan University between September 2021 and December 2023. All patients were administered with concurrent and adjuvant temozolomide. Eleven patients received adjuvant TTFields after surgery. Information regarding patient baseline characteristics, treatment approaches and molecular markers were collected with the purpose of analyzing prognostic factors. RESULTS The median follow-up was 15.7 months. At the time of data cutoff of this analysis, 20 patients had tumor relapse; 3 patients died, all of them were without TTFields therapy. The most common tumor failure pattern was local recurrence (80%, 16/20). The median PFS for the entire cohort was 19.3 months, the median OS was not reached. Univariate analysis indicated that patients who received TTFields therapy tended to have longer median PFS than that of patients without TTFields therapy (24.4 months vs. 18.5 months, P=0.097). Additionally, patients younger than 40 years (24.4 vs. 18.5 months, P=0.107) or without homozygous deletion of CDKN2A/B (23.7 vs. 18.0 months, P=0.108) tended to have better median PFS. No significant independent prognostic factor was found in the multivariate analysis. CONCLUSIONS The overall prognosis of IDHmA4 is poor. TTFields may help to improve the outcome of patients with newly-diagnosed IDHmA4. Longer follow-up, larger sample size and prospective clinical trials are warranted for deeper comprehension.