Conventionally fractionated versus hypofractionated radiotherapy in elderly glioblastoma patients
Hye In Lee,
Korea Republic of
PD-0647
Abstract
Conventionally fractionated versus hypofractionated radiotherapy in elderly glioblastoma patients
Authors: Hye In Lee1, Jina Kim2, In Ah Kim3, Joo Ho Lee1, Hong In Yoon2, Chan Woo Wee4
1Seoul National University Hospital, Department of Radiation Oncology, Seoul, Korea Republic of; 2Yonsei Cancer Center, Department of Radiation Oncology, Seoul, Korea Republic of; 3Seoul National University Bundang Hospital, Department of Radiation Oncology, Seongnam, Korea Republic of; 4SMG-SNU Boramae Medical Center, Department of Radiation Oncology, Seoul, Korea Republic of
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Purpose or Objective
This study aimed to compare the outcomes of conventionally fractionated radiotherapy (CFRT) and hypofractionated radiotherapy (HFRT) in elderly glioblastoma (e-GBM) patients and identify subgroups who may benefit from CFRT.
Material and Methods
Patients aged 65 years or older underwent surgical resection and radiotherapy for newly diagnosed IDH-wildtype e-GBM between 2006 and 2021 were included in this multicenter cohort study. Patients who were planned for a ≥6-week or ≤4-week radiotherapy were regarded as being treated with CFRT or HFRT, respectively. The median radiotherapy dose in the CFRT and HFRT group were 60 Gy in 30 fractions and 45 Gy in 15 fractions, respectively. Median survival (MS) was calculated from the date of surgery.
Results
A total of 239 and 221 patients who underwent CFRT and HFRT were included, respectively. 84% of patients were treated with temozolomide (TMZ)-based chemoradiation. With a median follow-up of 17.7 months (range, 3.3–149.9) for survivors, the MS was 17.5 months for CFRT group and 13.5 months for HFRT group, respectively (p<0.001). In multivariate analysis, CFRT (vs. HFRT) was a significantly favorable factor for overall survival in both patients older than 65 years (p=0.020) and 70 years (p=0.021). TERT promoter mutation (p=0.028) and TP53 mutation (p<0.001) were significantly adverse genetic factors for survival. In patients with unmethylated MGMT promoters, TMZ marginally improved MS compared to RT alone (14.1 vs. 10.7 months; p=0.072) in univariate analysis. However, in multivariate analysis of these patients, only the use of CFRT over HFRT significantly improved MS (p=0.003). Finally, recursive partitioning analysis identified three prognostic subgroups; class I = MGMTmeth/KPS≥70; class II = MGMTmeth/KPS<70 or MGMTunmeth/GTR; class III = MGMTunmeth/residual disease (p<0.001). Compared to HFRT, CFRT significantly improved MS in class I (39.7 vs. 22.5 months; p=0.003) and class II (16.9 vs. 13.5 months; p=0.001), but not in class III (10.8 vs. 10.4 months; p=0.637).
Conclusion
Compared to HFRT, CFRT can be a more effective strategy for selected e-GBM patients. Further prospective studies are needed to establish an optimal guideline for e-GBM patients.