Study Highlights Limitations of Shorter Radiotherapy in Glioblastoma Treatment
A recent phase 3 trial has revealed critical insights into the efficacy of ultrahypofractionated radiotherapy for newly diagnosed glioblastoma patients. The study indicates that this treatment regimen correlates with a significantly shorter median overall survival period compared to the established standard fractionation approach. Specifically, ultrahypofractionated radiotherapy resulted in a median survival of 13 months, markedly less than the 21 months observed with standard treatment protocols.
The research, conducted across eight radiotherapy centers in the Netherlands, included 135 adults with newly diagnosed glioblastoma. Participants were randomized to receive either ultrahypofractionated radiotherapy (6 × 6 Gy over two weeks) or the standard schedule (30 × 2 Gy over six weeks), both with temozolomide, concurrently and as adjuvant therapy. Despite initial phase 2 studies suggesting potential parity with the standard fractionation in terms of survival outcomes, these new findings refute such equivalence.
A crucial aspect of the trial focused on the two-year overall survival rate, assessing noninferiority with a predefined hazard ratio margin. Unfortunately, the trial’s recruitment was terminated prematurely due to enrollment challenges exacerbated by the COVID-19 pandemic, limiting the study sample to 135 of the originally planned 474 participants. This limitation, alongside nonproportional hazard observations, posed challenges to conclusively determining treatment noninferiority.
In the trial's outcome analysis, the ultrahypofractionated group showed a 1-year survival rate of 52.2%, as opposed to 70.6% in the standard treatment group. Progression-free survival (PFS) also reflected these disparities, highlighting a median of 10 months for the standard treatment and 9 months for the ultrahypofractionated schedule. The incidence of radiation-induced necrosis or pseudoprogression was significantly higher in the experimental arm, occurring in 47.8% of patients compared to 16.2% in the control group. Despite these challenges, no severe grade 4-5 toxicities were reported in either cohort.
Authors of the study, led by Anouk M. de Jong from the University Medical Center Utrecht, concluded that the ultrahypofractionated protocol should not replace the current standard chemoradiation due to its inferior survival outcomes and increased risk of radiation necrosis. Their findings were published on August 8 in the journal Radiotherapy and Oncology.
Funding for the research was provided by ZonMw, The Netherlands Organisation for Health Research and Development. It is important to note that ZonMw did not influence the study's design or publications. Additionally, Joost J.C. Verhoeff, one of the researchers, reported financial support from the same organization.
These findings underscore the importance of ongoing research to optimize glioblastoma treatment protocols and highlight potential avenues for future studies to address the survival and quality-of-life concerns faced by patients with this aggressive cancer.