GLOW Study Ends – But WGS Remains Valuable for Glioblastoma Patients

As of October 1, 2025, the GLOW study will officially come to an end. Interim analysis has shown growing enthusiasm among medical specialists for using comprehensive molecular diagnostics in this patient group. Despite identifying potential targets for personalized treatment through Whole Genome Sequencing (WGS), only a few patients actually started such targeted therapies. As a result, the primary aim of the study – demonstrating an improvement in survival – is no longer attainable. 

GLOW Results 

The interim analysis of the GLOW study (based on 160 patients) demonstrated that Whole Genome Sequencing (WGS) is feasible in 80% of patients, and potential treatment targets were identified in 32% of cases. However, only a few patients eventually started targeted therapy. The main reasons for not initiating targeted (clinical trial) treatments were the absence of an open study or cohort for the specific target at the time, or the treating physician deemed the target not actionable. 

What Does This Mean for Glioblastoma Patients? 

The conclusion of the GLOW study does not mean the end of access to Whole Genome Sequencing (WGS) for glioblastoma patients. In fact, as of June 24, 2025, WGS has been included in the basic healthcare package by the Dutch National Health Care Institute (Zorginstituut Nederland) – including for the detection of NTRK fusions in second-line treatment. 

We encourage healthcare professionals to actively raise this within their hospitals and in discussions with health insurers. The existing Service Agreement (Dienstverleningsovereenkomst, DVO) under which GLOW operated can generally continue to be used. For questions regarding logistics or billing, please contact Desiree van der Kleij at the Hartwig Medical Foundation. 

Next Steps: Targeted Therapy & PePPer Study 

There is strong interest in using WGS for patients with recurrent glioblastoma, and treatable cancer types are regularly identified. To further improve access to targeted therapies, the nationwide PePPer study has recently been approved. More information on this will follow soon. 

Summary 

Although the GLOW study is ending, it has provided valuable insights. WGS remains available as part of standard care for patients with primary brain tumors. With the launch of the PePPer study, we are taking the next step together toward better access to personalized treatments.