Radiation and Chemotherapy

KEY FACTS

TERMINOLOGY

• Radiation-induced injury may be divided into acute,

subacute/early delayed, late injury

IMAGING

• Radiation injury: Mild vasogenic edema to necrosis

• Radiation necrosis: Irregular enhancing lesion(s)

○ MRS: Markedly ↓ metabolites (NAA, Cho, Cr), ±

lactate/lipid peaks

○ Perfusion MR: ↓ relative cerebral blood volume

compared with tumor

• Leukoencephalopathy: T2 white matter (WM)

hyperintensity, spares subcortical U fibers

• Mineralizing microangiopathy: Basal ganglia, subcortical

WM Ca++, atrophy

• Necrotizing leukoencephalopathy: WM necrosis

• PRES: Posterior circulation subcortical WM edema

• MRS, MR perfusion, PET, or SPECT may help delineate

recurrent tumor from radiation necrosis

TOP DIFFERENTIAL DIAGNOSES

• Neoplasm

• Abscess

• Multiple sclerosis

• Vascular dementia

• Progressive multifocal leukoencephalopathy

PATHOLOGY

• 2nd neoplasms: Meningiomas (70%), gliomas (20%),

sarcomas (10%)

○ More aggressive tumors, highly refractory

○ Incidence: 3-12%

• Radiation-induced vascular malformations: Capillary

telangiectasias ± cavernomas

CLINICAL ISSUES

• Overall incidence of radionecrosis: 3-9%

• Worse prognosis: Younger patient at treatment

(Left) Axial NECT shows

extensive calcification in the

subcortical white matter (WM)

﬉ in a 20-year-old patient.

Mineralizing microangiopathy

usually results after a

combination of radiation

therapy and chemotherapy 2

or more years after treatment.

(Right) Axial SWI in an adult

patient with

neurofibromatosis and optic

nerve glioma status post

radiation therapy in childhood

shows innumerable

"blooming" hypointense foci

﬈ consistent with radiationinduced vascular

malformations.

(Left) Axial FLAIR MR in a 22

year old with acute leukemia

treated with intrathecal

methotrexate shows confluent

periventricular and deep WM

hyperintensities ﬉ with

sparing of the subcortical WM.

(Right) Axial T1 C+ MR in the

same patient shows multiple

nodular enhancing lesions in

the WM ﬈. Findings are

consistent with

chemotherapy-induced

necrotizing

leukoencephalopathy.

Leukoencephalopathy is a

potentially serious

complication of

chemotherapy.

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

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