2588 - Benefit of Reirradiation in Recurrent Glioblastoma after Temozolomide-Based Chemoradiation: A Secondary and Updated Analysis of the [BLINDED] Study

S. Park¹, H. I. Yoon², D. Kim³, J. H. Lee⁴, N. Kim⁵, D. H. Lim⁶, J. H. Song⁷, C. O. Suh⁸, C. W. Wee², and I. A. Kim⁹; ¹Department of Radiation Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Korea, Republic of (South), ²Department of Radiation Oncology, Yonsei Cancer Center, Heavy Ion Therapy Research Institute, Yonsei University College of Medicine, Seoul, Korea, Republic of (South), ³Department of Radiation Oncology, Chungnam National University Hospital, Chungnam National University College of Medicine, Daejeon, Korea, Republic of (South), ⁴Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea, Republic of (South), ⁵Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea, Republic of (South), ⁶Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea, Republic of (South), ⁷Department of Radiation Oncology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South), ⁸Department of Radiation Oncology, Bundang CHA Medical Center, CHA University, Gyeonggi-do, Korea, Republic of (South), ⁹Department of Radiation Oncology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea, Republic of (South)

Purpose/Objective(s): To evaluate the role of reirradiation (re-RT) in patients with IDH wildtype recurrent glioblastoma (rGBM) after standard temozolomide-based chemoradiation. Materials/

Methods: Among 531 patients with IDH wildtype rGBM enrolled in the [BLINDED] study, 286 patients who underwent re-operation (re-OP, n=166) or re-RT (n=206) or both were analyzed for their overall survival. A comprehensive analysis was done incorporating clinical factors as well as genetic biomarkers.
Results: Median OS was 13.4 months in the re-OP group and 10.9 in the re-RT group. In the re-OP group, higher Karnofsky Performance Status (KPS), gross total resection (GTR), and postoperative re-RT improved survival, while out-field recurrence and homozygous deletion of CDKN2A/B were poor prognostic factors. Subgroup analysis showed that in patients undergoing re-OP, those with homozygous CDKN2A/B deletion, TERT promoter mutation, KPS =80, or recurrence-free interval =12 months benefited the most with re-RT. Stratification based on these factors into re-RT favorable (2-4 factors) and unfavorable groups (0-1 factors) showed re-RT significantly improved median OS in the favorable group (23.3 vs. 13.4 months, p=0.003), but did not in the unfavorable group. Predictors of better survival in all patients who received re-RT were KPS =80, age =60, and gross total resection, while EGFR gene amplification and TP53 gene mutation were negative indicators (all P<0.05). Risk factors of grade 2 or higher radiation necrosis after re-RT were infield/marginal recurrence and no prior re-OP.
Conclusion: The addition of re-RT significantly improved overall survival in rGBM patients undergoing re-OP, highlighting the importance of personalized treatment strategies. This study identifies specific patient subgroups that would benefit most from re-OP and re-RT, emphasizing the need for tailored therapeutic approaches in these patients.