The goal of this observational study is to identify biomarkers of treatment-induced brain injury in children treated for primary brain tumors. The main question it aims to answer is:

Can investigators identify sensitive plasma biomarker(s) of treatment-induced brain injury in children with primary brain tumors?

Researchers will compare results between different treatment modalities (surgery, chemotherapy, radiation versus radiation-naive) and a healthy age- and sex-matched control population, to identify treatment-specific biomarkers.

Participants will provide plasma samples at the following time points: before surgery, 1-2 weeks after surgery, as well as at 3-, 6-, 12-, 18-, 24-, and 36 months after surgery. Participants who receive radiation treatment will also provide plasma samples before and during treatment (approximately every 2 weeks). Where possible, plasma samples are also collected before the start of any new treatment (e.g., chemotherapy). Healthy controls will provide samples once.

Inclusion Criteria, Group A (treated with radiation):

• Age 0-17 years old, AND
• Diagnosed with primary brain tumor through surgery, biopsy, or other diagnostic method (e.g., for germinoma) at Uppsala University Hospital or at another university hospital in Sweden, AND
• Referred for radiotherapy at Skandion Clinic in Uppsala and/or at their local hospital (in some cases), with/without the addition of other cancer treatments.

Inclusion Criteria, Group B (treated without radiation/radiation naive):

• Age 0-17 years old, AND
• Diagnosed with primary brain tumor through surgery, biopsy, or other diagnostic method (e.g., for optic pathway glioma in neurofibromatosis type 1 and germinoma) at Uppsala University Hospital or at another university hospital in Sweden, AND
• Not referred to radiotherapy and treated with/without the addition of other cancer treatments.

Inclusion Criteria, Group C (healthy control group):

• Age 0-17 years old at time of recruitment

Exclusion Criteria, Groups A + B:

• Diagnosed with a tumor only in the spinal cord (solitary spinal tumor).
• Diagnosed with a tumor considered palliative already at diagnosis (e.g., diffuse intrinsic pontine glioma)

Exclusion Criteria, Group C:

• Have diagnosis of chronic disease that requires continuous medication.

Exclusion Criteria, all groups:

• Unable to provide informed consent due to language difficulties.

Groups A and B will be selected from all children, 0-17 years of age, in Sweden with primary (newly diagnosed) brain tumors.

Group C will be selected from:

• Healthy sibling controls to other study participants, OR
• Siblings to other children admitted to Uppsala University Hospital, OR
• Other healthy children for example those who attend Uppsala University Hospital for another reason (e.g., minor elective daycare surgery).

Data can only be shared upon reasonable request, with appropriate approvals in place.