What is the standard radiotherapy approach for a non‑resectable focal low‑grade brain‑stem glioma in a patient with Karnofsky performance status ≥70 and no prior cranial irradiation?

Radiotherapy for Focal Brain Stem Glioma

For a non-resectable focal low-grade brainstem glioma in an adult with good performance status (Karnofsky ≥70), radiotherapy should be offered as a treatment option, particularly if the tumor shows clinical or radiological progression. 1

Treatment Algorithm Based on Tumor Characteristics

For Focal Exophytic Lesions (Non-resectable)

• Biopsy or resection should be considered first to establish histology, as this guides subsequent management decisions 1
• If biopsy confirms low-grade histology and optimal resection remains impossible, the treatment options include: radiotherapy, follow-up alone, or biopsy with radiotherapy 1
• The choice depends on age, histology results, and MRI characteristics 1

Radiotherapy Indications and Approach

• Radiotherapy should be reserved for progressive tumors diagnosed by clinical symptoms and/or radiological progression 1
• Localized (focal) radiotherapy is the standard approach, not craniospinal irradiation 1
• The recommended dose range is 45-54 Gy, with 50-54 Gy preferred for low-grade gliomas 1
• For focal brainstem lesions specifically, focal fractionated radiotherapy to the tumor bed is appropriate 2

Critical Decision Points

When to Treat vs. Observe

The guideline evidence explicitly states that there is no standard treatment for focal brainstem gliomas 1, making this a clinical judgment based on:

• Patient clinical status must be considered in any treatment decision 1
• Only progressive tumors should be treated with radiotherapy 1
• Stable, asymptomatic focal lesions may be managed with follow-up alone 1

Prognostic Factors Favoring Treatment

For low-grade gliomas generally, poor prognostic factors that favor earlier intervention include 1:

• Age >35-40 years
• Low Karnofsky score (<70)
• Functional deficits or intracranial hypertension
• Large or rapidly increasing tumor volume
• Contrast enhancement on MRI
• Uncontrolled epilepsy

Alternative and Salvage Options

Stereotactic Radiosurgery

• Gamma Knife radiosurgery has shown efficacy as primary treatment for focal low-grade brainstem gliomas, with some evidence suggesting 5-year local control rates of 66% 3
• This approach may be particularly suitable for small, well-defined focal lesions 3

Re-irradiation at Progression

• If progression occurs after initial radiotherapy, re-irradiation with hypofractionated stereotactic techniques (16-25 Gy in 2-5 fractions) can provide additional months of survival 4
• Four of five adult patients in one series achieved 3-14 months of additional survival with re-irradiation 4

Chemotherapy After Radiotherapy Failure

• Chemotherapy should only be considered after radiotherapy failure, not as primary treatment 1
• Temozolomide (150-200 mg/m² days 1-5 of 28-day cycles) showed 60% clinical improvement and median progression-free survival of 9.5 months in adults with recurrent low-grade diffuse brainstem gliomas after radiotherapy failure 5

Common Pitfalls to Avoid

• Do not administer craniospinal irradiation for focal lesions—localized radiotherapy is the standard 1
• Do not treat stable, asymptomatic lesions with radiotherapy—reserve treatment for progressive disease 1
• Do not use chemotherapy as first-line treatment—radiotherapy is the established option for progressive disease 1
• Do not assume all brainstem gliomas behave identically—focal lesions in adults have better prognosis than diffuse lesions and pediatric counterparts 6

Surveillance Strategy

• MRI should be used for both diagnosis and follow-up 1
• For patients on observation, annual clinical and MRI follow-up over many years is appropriate 1
• Adult brainstem gliomas have median survival of approximately 5 years with radiotherapy for diffuse low-grade forms 6