ESTRO 2024 - Abstract Book

S800

Clinical - CNS

ESTRO 2024

and 25 (9.92%) patients in standard STUPP and PERRY regimens respectively, while, 56 (22.22%) patients received radiotherapy with no chemotherapy.

Median follow up was 13 months. Median overall survival (OS) of the whole cohort was 14 months (95% CI: 13-15), 214 patients died. Median disease-specific survival (DSS) was 14 (13-16), with 212 cancer-related deaths observed.

Kaplan-Meier survival analysis showed significantly reduced OS and DSS in patients taking any antibiotic regardless of oncological treatment (OS: Median/95% CI (months): 12/11-14 vs. 16/14-21, p=0.003; DSS: 12/11-14 vs. 16/14-21, p=0.004). To further explore this relationship, the effect of a number of antibiotic courses was assessed. Patients receiving 2 or more courses (2+) had worse OS, with median OS/95% CI of 12/9-15 vs. 13/11-17 vs. 16/14-21 (p=0.003) for 2+, 1, or no courses of antibiotics, respectively. Cox regression showed that antibiotic exposure was independently associated with reduced OS/DSS (OS: HR 1.47, 95%CI: 1.117-1.947, p=0.006; DSS: 1.44, 1.092-1.909, p=0.0099). Subgroup Kaplan-Meier modelling showed that the benefit on survival was significant when restricting analysis to only patients receiving 60Gy/30 fractions (OS: p=0.0018; DSS: p=0.0025, or only patients receiving concurrent chemotherapy (p=0.00044), but was not significant in 40Gy/15# (0.8) or in omission of chemotherapy (p=0.8).

Conclusion:

Antibiotic exposure may reduce the efficacy of GBM treatment. Ongoing research will validate these findings. This effect may be mediated by gut microbiota, the intra-tumoural microbiota or both, as well as by non-microbiota related antibiotic medication effects.

Keywords: Microbiome, Glioblastoma, Antibiotics

References:

1, Nenclares P et al., Impact of antibiotic use during curative treatment of locally advanced head and neck cancers with chemotherapy and radiotherapy. Eur J Cancer. 2020. May:131:9-15

2. Reis Ferreira M et al., The microbiota and radiotherapy for head and neck cancer: What should clinical oncologists know? Cancer Treat Rev. 2022 Sep:109:102442

896

Mini-Oral

Risk of vertebral compressive fracture in elderly patients treated with spine SBRT

Adrian Wai Chan 1 , K. Liang Zeng 2 , Sten Myrehaug 1 , Hany Soliman 1 , Chia-Lin Tseng 1 , Hanbo Chen 1 , Eshetu G Atenafu 3 , Arjun Sahgal 1 , Jay Detsky 1