The benefit of surveillance imaging for paediatric cerebellar pilocytic astrocytoma

Paediatric cerebellar pilocytic astrocytomas (PA) (WHO grade 1) are amongst the most common of childhood brain tumours and are generally amenable to resection, with surgery alone being curative in the majority of cases. There is, however, a lack of consensus regarding the frequency and duration of post-treatment MRI surveillance for these tumours. This is important, as follow-up imaging is a significant use of resources and often associated with patient and family anxiety. We have assessed the utility of MRI surveillance in the detection of cerebellar PA recurrence at our regional paediatric neurosurgical centre.

The tumour register at Alder Hey Children's Hospital was searched to identify all patients diagnosed between 2007 and 2017, with a confirmed histopathological diagnosis of cerebellar PA. Patient demographics, surgical outcome, number of MRI scans and length of follow-up were recorded for each patient.

Forty patients met the inclusion criteria. The mean age at diagnosis was 7.8 years (range 2 to 17 years). Complete surgical resection (CR), confirmed by post-operative MRI, was achieved in 36 of the 40 patients, including all 31 cases from 2009 and later for which intraoperative MRI (iMRI) was utilised. There was one case of recurrence after CR (at 2.2 years) out of the 36 cases, whereas all 4 patients with initial partial resections had progressive growth of their tumours and required second surgical interventions.

This series confirms the very low likelihood of recurrence for completely resected cerebellar PAs and suggests that in such cases the duration and frequency of surveillance imaging could be limited to a maximum of 2.5 to 3 years of follow-up imaging. This report also indicates improved complete resection rates over time, probably associated with technical advances including the routine in-house use of iMRI in 2009.