603P - An individualised postoperative radiological surveillance schedule for IDH-wildtype glioblastoma patients (HK-GBM Registry)

Background

Glioblastoma is a malignant brain tumour with a high recurrence rate following stanadard first-line treatment. While there are currently guidelines from NICE and EANO on the postoperative surveillance intervals for these patients, they were not evidence-based, and the quality of such recommendations remains untested. We therefore set out to provide an evidence-based recommendation on the optimal postoperative radiological surveillance schedule for glioblastoma patients after surgical treatment, tailored based on the extent of surgical resection and completion of adjuvant treatment.

Methods

This was a territory-wide, multicentre retrospective analysis of consecutive adult patients with IDH-wildtype glioblastoma treated with surgery and radiotherapy (RT) across seven neurosurgical units in Hong Kong between 2006-2020 (n=228). Data were extracted from the Hong Kong Glioblastoma Registry (HK-GBM Registry). Interval-censored Kaplan-Meier curves were constructed for the stratified groups based on the event-free survival of included patients, defined as time from the start date of RT to the occurrence of any event (tumour progression or death). A piecewise exponential model with different hazard functions in predefined time intervals was used to describe each curve. Accordingly, adopting a 15% event rate criterion, we generated the surveillance schedules.

Results

For a 15% event yield each scan (15% event rate criterion), we propose that glioblastoma patients treated with gross total resection be monitored with MRIs around every 9 weeks until 86 weeks after starting RT. Meanwhile, patients with residual tumour after surgery should be monitored more frequently at every 7 weeks until 75 weeks after RT initiation; and the interval should be further shortened to every 4 weeks for patients who were unable to complete the standard 6-weeks concurrent chemoradiotherapy.

Conclusions

Radiological surveillance is an important tool to detect postoperative tumour progression. The extent of surgical resection and completion of adjuvant treatment are major factors associated with glioblastoma progression and the frequency of radiological surveillance should therefore be guided by these two factors.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The Hong Kong Neuro-oncology Society.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.