Top Line: Standard salvage treatments for glioblastoma (GBM) don’t have robust data backing them up.
The Study: A common strategy is reirradiation with concurrent bevacizumab. Such antiangiogenic agents are thought to overcome hypoxia-induced radioresistance. RTOG 1205 is the first randomized trial to evaluate re-irradiation with modern techniques. 170 enrollees receiving bevacizumab 10 mg/kg every 2 weeks until progression were randomized to +/- the addition of reirradiation to 35 Gy in 10 fractions. Sadly the primary endpoint of overall survival was not improved with the addition of radiation with a median survival of 10 months either way. While this is disappointing, lack of a demonstrable benefit may be a result of extremely broad inclusion criteria. “In response to low accrual, NRG Oncology/RTOG1205 was amended to broaden eligibility, resulting in the inclusion of a significant number of patients less likely to benefit from focal, re-RT because of extensive disease burden.” In fact, the only subgroup that did have a significant survival advantage with reirradiation were those with a KPS 90-100 (HR 0.67). Others with standout survival included those receiving reirradiation for first recurrence, longer time interval to reirradiation, and smaller target volumes. There was also a clear improvement in recorded progression-free survival across all enrollees with a median of 4 months without reirradiation and 7 months with, which the authors point out is typically correlated with better neurocognitive outcomes and less steroid requirements (though neither were reported here).
TBL: Reirradiation for recurrent GBM treated with bevacizumab helps delay progression but does not improve survival across all-comers. | Tsien, J Clin Oncol 2022