When Surgical Innovation Outpaces Evidence: Does Modern Maximal Resection Require Re-Evaluation of Postoperative...

Area of Science:

• Neuro-oncology
• Radiation Oncology
• Clinical Trial Design

Background:

• Postoperative radiotherapy (RT) is a standard glioblastoma treatment, established by trials before advanced imaging, molecular diagnostics, and temozolomide (TMZ).
• These historical trials utilized whole-brain or large-field RT in heterogeneous patient groups, yielding a pooled survival benefit (RR 0.81).
• Modern glioblastoma management includes improved surgical techniques, MRI, molecular classification (e.g., IDH-wildtype), and systemic therapies (e.g., TMZ), creating a distinct best-prognosis subgroup.

Purpose of the Study:

• To critically appraise the directness of existing randomized evidence for RT in glioblastoma using GRADE criteria.
• To develop a roadmap for designing future clinical trials focused on de-escalating RT in select glioblastoma patient populations.
• To address the unresolved question regarding the magnitude of RT benefit in the context of maximal contemporary glioblastoma therapy.

Main Methods:

• Structured appraisal of landmark randomized controlled trials (RCTs) using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) framework.
• Analysis of indirectness across population, intervention, comparator, and outcome domains in historical RT trials.
• Review of modern RT versus no-RT evidence, noting its derivation from elderly patient cohorts.

Main Results:

• Historical glioblastoma RT trials exhibit substantial indirectness when applied to contemporary patient populations and treatments.
• The only modern RT vs. no-RT evidence comes from elderly patients, representing a different prognostic spectrum.
• The infiltrative nature of glioblastoma, typical in-field recurrence patterns, and radioresistant cancer stem cells suggest RT remains biologically plausible.

Conclusions:

• There is significant indirectness in the evidence supporting postoperative RT for the modern glioblastoma best-prognosis subgroup.
• Scientific equipoise exists regarding the precise magnitude of RT benefit with current maximal therapies and the potential for de-escalation strategies.
• Future de-escalation trials are warranted to prospectively evaluate reduced RT strategies in carefully selected glioblastoma patients.