Radiation Oncology: A Question-Based Review

12
Brainstem Glioma

Steven H. Lin and Ori Shokek

image Background


What is the prevalence of brainstem gliomas (BSGs) in relation to pediatric CNS tumors overall?

BSGs comprise 10% of pediatric CNS tumors (<2% of adult CNS tumors).

What is the peak age of presentation for BSGs? What is the gender predilection?

The peak age of BSG presentation is 5–9 yrs. Males are more commonly affected than females.

What are the 2 classes of BSGs? Where are they most commonly located, and what is the prognosis?

The 2 classes of BSGs are focal and diffuse.

1.     Focal (30%): in the upper midbrain/lower medulla; best prognosis

2.     Diffuse (70%): in the pons and upper medulla; infiltrative and worst prognosis

What BSG histology most commonly involves the medulla? The midbrain?

Glioblastoma multiforme in the medulla; grade 2 or 3 astrocytoma in the midbrain

Why does adult BSG tend to have a better prognosis?

Lesions in adults tend to be mostly low grade.

What is the median OS of BSG in adults vs. children vs. the elderly?

1.     Adults: 7.3 yrs

2.     Children: 1 yr

3.     The elderly: 11 mos

4.     Overall, the Dz is fatal in >90% of pts.

image Workup/Staging


What are some typical clinical findings with diffuse pontine glioma?

Typical findings with diffuse pontine glioma:

1.     CN palsy (CNs VI−VII)

2.     Ataxia

3.     Long tract signs (hyperreflexia, etc.)

What is the typical workup for a child with a suspected BSG?

Suspected BSG workup for a child: H&P, labs, MRI, typically no Bx

When should Bx be done for BSG?

When mass lesions have an unusual MRI appearance or there is an atypical clinical course (either possible benign tumors or an infectious/inflammatory etiology)

How is BSG staged?

There is no formal staging of BSG.

image Treatment/Prognosis


What is the typical Tx paradigm for BSG?

BSG Tx paradigm: steroids/shunts → RT alone +/− chemo with temozolomide (TMZ)

What type of BSG is amenable to surgical resection +/+ adj RT?

Dorsally exophytic BSGs have a 10-yr OS with surgery +/− RT in 75% of pts. These are usually juvenile pilocytic astrocytomas (JPAs) with a good prognosis.

What is the typical RT dose for BSGs?

The typical RT dose for BSGs is 54 Gy in 1.8−2 Gy/fx.

What proportion of BSG pts will have stabilization or improvement of Sx after RT?

After RT, two thirds of pts will have stabilization or improvement of Sx.

Is there a role for hyperfractionation or dose escalation in BSG?

No. Both did not improve survival in multiple Pediatric Oncology Group/Children's Cancer Group (POG/CCG) trials (only better radiographic response at higher doses, however, with greater radionecrosis and long-term steroid dependence).

Is there any benefit with chemo in BSG?

No. There is very minimal response with single, combination, or high-dose/stem cell rescue.

Is there a role for TMZ after RT? How about concurrently with RT?

No (Broniscer A et al., Cancer 2005). MS is 12 mos. Concurrent TMZ is being tested in a COG phase II trial.

Is there a role for brachytherapy or Gamma Knife boost after RT in BSG?

No. There is no role for brachytherapy or Gamma Knife boost after RT.

How are tectal plate tumors managed? What is their histology?

Tectal plate tumors are managed with observation and a ventriculoperitoneal shunt for obstruction. They are typically JPAs (indolent).

What are the major prognostic factors dictating outcome in pts with BSGs?

Diffuse vs. focal, adult vs. child, and histology

What is the survival of pts with diffuse vs. focal BSG lesions?

1.     Diffuse: 12 mos (median)

2.     Focal: 10-yr OS ~50%−70%

What usually causes death in pts with BSGs?

Local expansion usually causes death in pts with BSGs.

image Toxicity


What is the RT dose tolerance of the brain stem?

The dose tolerance of the brain stem is 54 Gy (if fractionated EBRT) and 12 Gy (if SRS).