• Patients must be \>= 2 years and =\< 21 years at the time of enrollment

• Patients must have a body surface area (BSA) of \>= 0.5 m\^2 at enrollment

• Patients must have neurofibromatosis type 1 (NF1) based on clinical criteria and/or germline genetic testing

• Patients must be newly diagnosed or have previously diagnosed NF-1 associated LGG that has not been treated with any modality other than surgery

• For patients with optic pathway gliomas (OPGs):

‣ Newly-diagnosed patients with OPG are eligible if there are neurologic symptoms (including visual dysfunction, as defined below) or other exam findings associated with the tumor

⁃ Previously-diagnosed patients with OPG are eligible if they have new or worsening neurologic symptoms (including visual dysfunction, as defined below) or have tumor growth

⁃ For both newly-diagnosed and previously-diagnosed OPG, the patient may be eligible, irrespective of whether there has been tumor growth or other neurological symptoms or worsening, if they meet at least one of the following visual criteria:

• Visual worsening, defined as worsening of visual acuity (VA) or visual fields (VF) documented within the past year (by examination or history); OR

∙ Significant visual dysfunction (defined as VA worse than normal for age by 0.6 logMAR \[20/80, 6/24, or 2.5/10\] or more in one or both eyes)

• For patients with LGG in other locations (i.e., not OPGs):

‣ Newly-diagnosed patients with LGG are eligible if there are neurologic symptoms or other exam findings associated with the tumor

• NOTE: Newly-diagnosed patients with LGG without associated neurologic symptoms or exam findings are not eligible

⁃ Previously-diagnosed patients with LGG are eligible if they have new or worsening neurologic symptoms or have tumor growth

• Although not required, if a biopsy/tumor resection is performed, eligible histologies will include all tumors considered LGG or low-grade astrocytoma (World Health Organization \[WHO\] grade I and II) by 5th edition WHO classification of central nervous system (CNS) tumors with the exception of subependymal giant cell astrocytoma

• Patients must have two-dimensional measurable tumor \>= 1 cm\^2

• Patients with metastatic disease or multiple independent primary LGGs are allowed on study

• Creatinine clearance or radioisotope glomerular filtration Rate (GFR) \>= 70 mL/min/1.73 m\^2 OR a serum creatinine based on age/sex (within 7 days prior to enrollment) as follows:

‣ Age; maximum serum creatinine (mg/dL)

⁃ 2 to \< 6 years; 0.8 (male) and 0.8 (female)

⁃ \>= 16 years; 1.7 (male) and 1.4 (female)

• Total bilirubin =\< 1.5 x upper limit of normal (ULN) for age (within 7 days prior to enrollment) (children with a diagnosis of Gilbert's syndrome will be allowed on study regardless of their total and indirect \[unconjugated\] bilirubin levels as long as their direct \[conjugated\] bilirubin is \< 3.1 mg/dL)

• Serum glutamate pyruvate transaminase (SGPT) (alanine aminotransferase \[ALT\]) =\< 3 x upper limit of normal (ULN) = 135 U/L (within 7 days prior to enrollment). For the purpose of this study, the ULN for SGPT is 45 U/L

• Albumin \>= 2 g/dL (within 7 days prior to enrollment)

• Left ventricular ejection fraction (LVEF) \>= 53% (or institutional normal; if the LVEF result is given as a range of values, then the upper value of the range will be used) by echocardiogram (within 4 weeks prior to enrollment)

• Corrected QT (QTc) interval =\< 450 msec by electrocardiography (EKG) (within 4 weeks prior to enrollment)

• Absolute neutrophil count \>= 1,000/uL (unsupported) (within 7 days prior to enrollment)

• Platelets \>= 100,000/uL (unsupported) (within 7 days prior to enrollment)

• Hemoglobin \>= 8 g/dL (may be supported) (within 7 days prior to enrollment)

• Patients with a known seizure disorder should be stable and should have not experienced a significant increase in seizure frequency within 2 weeks prior to enrollment

• Patients 2-17 years of age must have a blood pressure that is =\< 95th percentile for age, height, and sex at the time of enrollment. Patients \>= 18 years of age must have a blood pressure =\< 130/80 mmHg at the time of enrollment (with or without the use of antihypertensive medications).

‣ Note: Adequate blood pressure can be achieved using medication for the treatment of hypertension

• All patients must have ophthalmology toxicity assessments performed within 8 weeks prior to enrollment

• For all patients, an MRI of the brain (with orbital cuts for optic pathway tumors) and/or spine (depending on the site(s) of primary disease) with and without contrast must be performed within 8 weeks prior to enrollment

• For patients who undergo a surgery on the target tumor (not required), a pre- and post-operative\* MRI of the brain (with orbital cuts for optic pathway tumors) or spine (depending on the site(s) of primary disease) with and without contrast must also be performed. The post-operative MRI must be performed within 4 weeks prior to enrollment. If only a biopsy is performed, a post-operative MRI is not required and the pre-operative (op) MRI within 8 weeks of enrollment will be used as the baseline scan

‣ The post-operative MRIs should be performed ideally within 48 hours after surgery if possible

• Patients must have a performance status corresponding to Eastern Cooperative Oncology Group (ECOG) scores of 0, 1, or 2. Use Karnofsky for patients \> 16 years of age and Lansky for patients =\< 16 years of age

• Patients must have the ability to swallow whole capsules

• Patients must have receptive and expressive language skills in English, Spanish or French to complete the quality of life (QOL) and neurocognitive assessments

• All patients and/or their parents or legal guardians must sign a written informed consent.

• All institutional, Food and Drug Administration (FDA), and National Cancer Institute (NCI) requirements for human studies must be met.