The Use of 5-Aminolevulinic Acid to Assist Gross Total Resection of Paediatric Posterior Fossa Tumours

Abstract

Background: 5-aminolevulinic acid (5-ALA) use is well established in the resection of adult high-grade gliomas. There is growing interest in its usefulness in the paediatric population. The potential benefit of 5-ALA-guided resection motivated our unit to offer the established adult protocol as off-label use.

Objective: to determine if 5-ALA guided resection was routinely useful and offered increased gross total resection (GTR) results.

Methods: Nineteen patients harbouring a posterior fossa tumour suggestive of either an ependymoma or medulloblastoma (MB) underwent surgery between January 2018 and October 2019. The mean age was 5 years (range 2-12 years). A dose of 20 mg/kg of 5-ALA (Gliolan®) was given 4 h preoperatively. Intraoperatively, the tumours were viewed under violet-blue light and the presence of fluorescence was recorded. Fluorescence status was compared with histopathological classification and grade, Ki-67 index, GTR rate, and a subjective determination of "usefulness" was determined.

Results: The case series included ependymoma grade II (n = 6), ependymoma grade III (n = 4), and MB grade IV (n = 9). For the combined cohort, the strong fluorescence rate was 68% (n = 13), the heterogenous fluorescence rate was 26% (n = 5), and the completely negative fluorescence rate was 5% (n = 1). The strong fluorescence rate of 90% found in the combined ependymoma group compared to the 45% strong fluorescence rate in the MB group was statistically significant (p = 0.05). Within the MB group the Ki-67 index was found to be significantly higher in the strongly fluorescent group as opposed to the patchy or non-fluorescent group (77.5 vs. 40%, p = 0.016). Fluorescence was determined to be useful in 63% of all cases. There was no significant relationship between fluorescence and GTR. The relationship between perceived usefulness and resection was not statistically significant. No adverse drug reactions were recorded.

Conclusion: This case series adds to the growing body of evidence demonstrating the safety of 5-ALA in the paediatric population. 5-ALA guided resection was found to be useful in the majority of cases but this did not correlate with GTR status. Ependymomas reliably fluoresce in 90% of cases, and 5-ALA-guided resection should be considered when a preoperative diagnosis of ependymoma is suspected.

Keywords: 5-aminolevulinic; 5-aminolevulinic acid; Brain tumour; Fluorescence.