10152-CS-14 Continued use of tumor treating fields after glioblastoma recurrence may contribute to prolonged survival

Abstract Background Recurrent glioblastoma carries a poor prognosis, with median overall survival (OS) of only 6-7 months despite optimal treatment. In Japan, tumor treating fields (TTF) are approved for newly diagnosed glioblastoma in adults. However, studies such as the EF-11 trial did not demonstrate a survival benefit in the recurrent setting, and post-recurrence TTF use is decided case by case. At our institution, approximately 40% of patients continue TTF after recurrence. We retrospectively compared outcomes between patients who continued TTF and those who discontinued it following radiographic recurrence. Methods We analyzed patients treated since 2017 who had used TTF for at least one month after initial diagnosis. Patients were grouped based on TTF continuation or discontinuation after recurrence. We compared median OS from TTF initiation and median OS after recurrence. Baseline characteristics including age, sex, TTF usage rate, time to recurrence, and performance status (PS) at recurrence were also evaluated. Results 14 patients continued TTF and 21 discontinued. Median OS from TTF initiation was longer in the continuation group (42 vs. 20 months), though not statistically significant (P = 0.09). Median OS after recurrence was significantly longer in the continuation group (20 vs. 10 months; P = 0.02). The continuation group had a higher proportion of younger patients (less than 60 years), higher TTF compliance (more than 75%), but these differences were not statistically significant. Conclusion While patients continuing TTF after recurrence may have had more favorable baseline factors, their survival outcomes were notably better, with median OS of 42 months from TTF initiation and 20 months after recurrence. These findings suggest that continued TTF use may offer a survival benefit in recurrent glioblastoma.