[Biopsy in the treatment of children with diffuse brainstem tumors]

Background. Diffuse brainstem tumors account for 10-20% of all brain tumors in children. These neoplasms are the leading cause of death in pediatric neuro-oncology. There are no effective treatments for this disease. Overall survival rarely exceeds 1.5-2 years.

Biopsy of diffuse brainstem tumors to determine their histological type and molecular genetic markers; to identify potential targets for targeted therapy.

In 2021-2025, 26 patients with diffuse brainstem tumors underwent surgery at the Morozovskaya Children's Clinical Hospital. Age of patients was 1.5-17 years, duration of disease - from 1 week to 13 months. There was primary tumor in 96% of cases. Preliminary diagnosis was based on clinical presentation and MRI. Stereotactic biopsy using BrainLab neuronavigator via transcerebellar approach was performed in 24 patients, open biopsy - in 2 cases.

The tumor was verified in 24 (92%) patients. Brain tissue was obtained from two patients. According to morphological data, 80% of patients had diffuse midline glioma. Ganglioglioma was detected in one case, high-grade glioma in one case, and low-grade glioma in one case. All patients underwent immunohistochemical examination of specimen, and 58% were examined using the NGS program. The H3K27M mutation was detected in 71% of cases, BRAF-V600E mutations in 2 patients, and FGFR2 gene mutation in 1 patient. Targeted therapy was based on information about mutations. The overall 2-year survival rate was 20%, event-free 2-year survival - 0%. Event-free survival of a patient with the BRAF-V600E mutation who received targeted therapy was 21 months.

Stereotactic biopsy of diffuse brainstem tumors can be performed safely. Identification of targets for personalized therapy may be essential for management of these patients.