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Washington and Leaver Chapter 35 Radiation Therapy Notes
- Course
- RADT (RAD242)
- Institution
- Wallace State Community College Hanceville
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Principles and Practice IIChapter 35:
BRAIN TUMORS:
- CNS cancers are the second most common cancers (20%) in children (after leukemia)
- Remain a leading cause of death, 5-year survival rates have gone from 63% to 75%
- Within the CNS, the brain is the most common site of disease
- Children are more frequently diagnosed with low-grade, infratentorial lesions when
compared with their adult counterparts
- Primitive neuroectodermal tumors (PNET) are also more common in younger ages (such
as medulloblastoma)
- Multidisciplinary approach
Low grade astrocytomas:
(astrocytomas are star shaped glial cells within the CNS)
- Exhibit slow, relentless growth and occur with equal frequency in the cerebrum and
posterior fossa
- Pilocytic low-grade lesions are the most common low-grade lesions in the pediatric group
- Present with nonspecific symptoms for years, headaches, degenerating coordination,
vision issues, and later seizures
- Well circumscribed and solid, often with a cystic component, less surrounding edema or
mass effect is found than with high-grade lesions
- Surgery is the mainstay of treatment
- If discovered in extremely young child with no neurologic defects, no immediate
treatment is required (wait until ages 3-5)
- 50-54 Gy is the typical dose
- 1.5cm for CTV + 0.5cm for PTV
High-grade astrocytomas:
(aka anaplastic astrocytomas and glioblastoma multiforme)
- Highly malignant and aggressive
- High-grade gliomas are typically supratentorial
- Rapidly progressing symptoms such as headaches, lethargy, motor or sensory loss,
seizures, and altered mental status
- Disrupt the BBB, have irregular borders, and contain areas of necrosis and surrounding
edema
- Neurosurgery first, multiple modalities
- Surgery provides immediate symptomatic relief, but residual tumor almost always
remains
, - Surgery goal of a complete resection, surgeon goal of maximum safe resection
compatible with good neurologic outcome
- Radiation treatment fields are large to encompass whole disease
- 3cm PTV, 45Gy-50Gy with boost bringing dose up to 54Gy-60Gy
- Overall, a poor prognosis
- Chemo is useful in infants to delay RT while the brain matures
Optic glioma:
- Low-grade, behave indolently, typically classified as grade 1 astrocytomas
- Visual disturbance is the most common presenting symptom
- Observation may be the initial strategy
- MRI is vital for treatment planning
- Tumors may be bilateral or track along the optic nerves, chiasm, and optic tracts
Ependymoma:
- Arise from cells that line the ventricles and may occur anywhere within the CNS
- Highest prevalence within the posterior fossa, arising from floor or roof of fourth
ventricle
- Presenting symptoms and pre-op imaging often mimic medulloblastoma, resulting from
increased intracranial pressure
- CSF seeding occurs in 5%-10% of all patients, more frequent in patients with
infratentorial and anaplastic ependymomas
- Gross total resection and post-op RT is the standard of care for ependymomas
- Extent of surgical resection is the most important prognostic factor
- CSI if seeding is noted
Medulloblastoma:
- Prototype posterior fossa malignancy and constitutes 20% of childhood brain tumors
- Type of PNET believed to arise from cerebellar stem cells
- Classic appearance is a “small, blue, round” cell that forms pseudorosettes
- Usually arises in the midline of the cerebellum and projects into the fourth ventricle and
brainstem
- 30%-35% of patients present with CSF seeding (mostly from anaplastic
medulloblastoma)
- Presenting symptoms occur within weeks or months, hydrocephalus may result from
decreased CSF flow to the fourth ventricle
- Headaches, morning vomiting, ataxia, cranial nerve abnormalities from invasion of the
brainstem
- MRI of the entire CNS and lumbar puncture to look for CSF seeding
- Maximal tumor resection is vital to good outcomes, posterior occipital craniotomy is used
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