ESTRO 2024 - Abstract Book

S2061

Clinical - Paediatric

ESTRO 2024

Purpose/Objective:

Low grade gliomas (LGG) are some of the most common brain tumours in children, teenagers and young adults. Radiotherapy may be considered, often following surgery and/or chemotherapy if the tumour grows despite prior treatment. Pseudoprogression can occur following radiotherapy in LGG (1,2). This study aims to evaluate the incidence of pseudoprogression in patients with LGG treated with PBT as well as clinical outcomes. We define pseudoprogression as per RANO criteria of transient tumour enhancement (3) or enlargement including cystic changes (2).

Material/Methods:

A retrospective review of all patients with diagnoses of a LGG including pilocytic astrocytoma, pilomyxoid astrocytoma, oligodendroglioma, glioneuronal and tectal plate glioma who received PBT at the Christie between December 2018 to June 2022 was performed. Patients with spinal low grade glioma were excluded from analyses. The patients’ electronic records were interrogated to obtain information on clinical outcomes. Where possible, scans and letters from external hospitals were sought to extract data on disease control and pseudoprogression.

Results:

A total of 45 patients were identified, with a median follow-up time of 24 months (range: 1.2-41.3 months). The median age at treatment was 16 years (range: 3-25 years). Twenty-one patients (46.7%) were female and twenty four (53.3%) male. Thirty-three patients had pilocytic astrocytoma, four oligodendroglioma, three pilomyxoid, one glioneuronal and four low grade glioma (unspecified). Thirty-four (75.6%) patients had supratentorial tumours and eleven patients (24.4%) had infratentorial tumours. The supratentorial tumours included tumours in the suprasellar region (6), optic chiasm/hypothalamus (6), as well as in the frontal lobe (2), temporal lobes (5), parietal lobe (3), thalamus (5), tectum (5), basal ganglia (1). The infratentorial tumours included tumours in the brainstem (3), cervico-medullary junction (3) and other posterior fossa locations (5). Only two patients had metastatic deposits at the time of tumour diagnosis and three additional patients had metastatic deposits at the time of PBT. Thirty-one patients (68.9%) had undergone at least one surgery prior to PBT. Twenty-nine patients (64.4%) did not receive any systemic treatment prior to PBT. Only two patients (4.4%) had 1 course of chemotherapy prior to PBT, while fourteen patients (31.1%) received >1 regimen prior to PBT. The total radiation dose received by patients ranged from 50.4-54Gy in 28-30 fractions. Twenty patients received 50.4Gy, two had 52.2Gy and twenty-three had 54Gy. Forty (88.9%) had focal radiotherapy whilst 5 (11.1%) received craniospinal radiotherapy. At the time of analysis, one patient with disease in the posterior fossa had died, with no evidence of local progression. Local control at 24-months median follow-up was 93.3%. Of the three patients (6.7%) who progressed locally, two had surgery post-PBT and one had chemotherapy. The incidence of pseudoprogression in our cohort was 31.1% (14/45). The median time to radiological pseudoprogression was 3.2 months (range 1.18-10.2). Six patients (13.3%) had an increase in tumour enhancement, and a further six had an increase in cystic swelling. In one patient, there was an increase in necrosis of the suprasellar mass radiologically. A patient who had tectal plate glioma developed a new satellite area of enhancement in the right medial thalamus, having received 54Gy. Five patients (11.1%) developed new or worsening hydrocephalus secondary to pseudoprogression. Four patients needed urgent neurosurgical