Table 1. Data collected on each patient and their definitions.

PS: performance status, 5-ALA: 5-aminolevulinic acid, MGMT: O(6)-methylguanine-DNA methyltransferase, IDH: isocitrate dehydrogenase.

Variable	Categories	Definition
Age	Continuous variable	Age at the time of surgery
Sex	Male	Male or female at birth
	Female
Radiotherapy	Received radiotherapy	Patient received standard radiotherapy treatment, as recorded in the clinical oncology notes.
	Did not receive radiotherapy
Chemotherapy	Received temozolomide	Patient received standard chemotherapy treatment with temozolomide, as recorded in the clinical oncology notes.
	Did not receive temozolomide
MGMT methylation	MGMT methylated	Tumour cells containing methylated MGMT, as reported in the pathology notes.
	MGMT not methylated
IDH 1/2 mutation	IDH 1/2 mutated	Tumour cells containing IDH 1/2 mutations, as reported in the pathology notes.
	IDH 1/2 not mutated
Anatomical location of tumour	Single lobe (frontal lobe, parietal lobe, occipital lobe, temporal lobe, cerebellum)	The location of the tumour as reported in the patient’s notes. Tumours were classified as ‘multiple lobes’ if the tumour extended into more than one lobe, as reported in the radiology notes.
	Multiple lobes
Treatment group	5-ALA	Resection was carried out under white light resection or using 5-ALA fluorescence-guided resection, as reported in the neurosurgery operation notes.
	White light
WHO performance status	Pre-operative WHO performance status	WHO performance status pre- and post-operatively, as reported in the patient’s notes. PS was also categorised into high (≥ 2) and low (≤ 1).
	Post-operative WHO performance status
Change in WHO performance status	Increase	The difference in WHO performance status between post-operative and pre-operative assessment, as recorded in the patient's notes.
	No change or decrease
Pre-operative neurological deficit	No deficit	Neurological deficit recorded pre-operatively in the patient's notes.
	Pre-operative deficit
New post-operative neurological deficit	No new post-operative deficit	Neurological deficit recorded post-operatively (in addition to pre-operative deficit) in the patient's notes.
	New post-operative deficit
Degree of resection	> 90% resection	Degree of resection of contrast-enhancing tumour on T1 MRI, measured using volumetric analysis on Picture Archiving Communications System (PACS) software, as reported by a radiologist in the patient’s notes.
	< 90% resection
Mortality (15 months)	Alive	Mortality at 15 months, calculated from the date of surgical resection.
	Deceased
Survival (days)	Continuous variable	Time to death, calculated in days, from the date of surgical resection. Censored at 15 months.