5-aminolevulinic acid is a non-fluorescent prodrug that leads to intracellular accumulation of fluorescent porphyrins in malignant gliomas—a finding that is under investigation for intraoperative identification and resection of these tumours. We aimed to assess the effect of fluorescence-guided resection with 5-aminolevulinic acid on surgical radicality, progression-free survival, overall survival, and morbidity.

322 patients aged 23–73 years with suspected malignant glioma amenable to complete resection of contrast-enhancing tumour were randomly assigned to 20 mg/kg bodyweight 5-aminolevulinic acid for fluorescence-guided resection (n=161) or to conventional microsurgery with white light (n=161). The primary endpoints were the number of patients without contrast-enhancing tumour on early MRI (ie, that obtained within 72 h after surgery) and 6-month progression-free survival as assessed by MRI. Secondary endpoints were volume of residual tumour on postoperative MRI, overall survival, neurological deficit, and toxic effects. We report the results of an interim analysis with 270 patients in the full-analysis population (139 assigned 5-aminolevulinic acid, 131 assigned white light), which excluded patients with ineligible histological and radiological findings as assessed by central reviewers who were masked as to treatment allocation; the interim analysis resulted in termination of the study as defined by the protocol. Primary and secondary endpoints were analysed by intention to treat in the full-analysis population. The study is registered at www.clinicaltrials.gov as NCT00241670.

Median follow-up was 35·4 months (95% CI 1·0–56·7). Contrast-enhancing tumour was resected completely in 90 (65%) of 139 patients assigned 5-aminolevulinic acid compared with 47 (36%) of 131 assigned white light (difference between groups 29% [95% CI 17–40], p<0·0001). Patients allocated 5-aminolevulinic acid had higher 6-month progression free survival than did those allocated white light (41·0% [32·8–49·2] vs 21·1% [14·0–28·2]; difference between groups 19·9% [9·1–30·7], p=0·0003, Z test). Groups did not differ in the frequency of severe adverse events or adverse events in any organ system class reported within 7 days after surgery.

Tumour fluorescence derived from 5-aminolevulinic acid enables more complete resections of contrast-enhancing tumour, leading to improved progression-free survival in patients with malignant glioma.