1. Pediatric Brain Tumor Genetics:
What Radiologists Need to
Know
Dr. Kannan G
Paediatric Radiologist
KMCH
2.
3. Radiogenomics
• imaging characteristics of a disease (also known as the imaging
phenotype) and the gene expression patterns, gene mutations, and
other genome-related characteristics (also known as the genetic
phenotype or genomics) of that disease
• Image phenotype vs genetic phenotype
• lateral cerebellar hemispheric medulloblastoma - sonic hedgehog
(SHH) subgroup
4. Radiomics
• defined as the high-throughput extraction of quantitative features
that results in the conversion of images into minable data and the
subsequent analysis of these data for decision support.
• The process of radiomics starts with delineating the region of interest,
that is, the tumor, in an imaging study and then extracting
quantitative data from the segmented volumes and entering them, as
well as other clinical and genomic data, into a database. This database
is subsequently mined, with use of artificial intelligence, machine
learning, and/or statistical analysis, to predict the diagnosis and
outcome
5.
6.
7. WHY
• diagnosis, management, and prognostication, all without the need to
first obtain a surgical specimen
• targeted therapy development, significantly affecting morbidity and
mortality rates.
• how aggressive the surgeon should be in trying to resect it, where to
obtain a biopsy specimen and which chemotherapeutic agent to
administer
• radiogenomics enables evaluation of the entire bulk of the tumor and
its stroma
9. Low-Grade Gliomas
• WHO grade I and II gliomas
• Pilocytic astrocytomas
• Other common histopathologic subtypes include gangliogliomas,
pleomorphic xanthoastrocytomas (PXAs), dysembryoplastic
neuroepithelial tumors, and diffuse astrocytomas.
• Pediatric LGGs have the smallest number of genetic alterations, with a
median of one mutation per tumor
12. Role of Imaging LGG
• Do not adhere to the rules established for adult gliomas
• Pilocytic astrocytoma - heterogeneous areas of avid enhancement,
and MR spectroscopy -low NAA and high choline and lactate
• DW-ADC map
• No vasogenic odema
• Pilocytic astrocytomas – midline, often seen in the posterior fossa
and along the optic pathway.
• Gangliogliomas -classically involve the cortex supratentorially
temporal lobe
13. Treatment Approach
• Complete resection
• Use of BRAF and MEK inhibitors
• BRAF inhibitors - dabrafenib and vemurafenib(BRAF
V600E mutation LGG)
• mTOR inhibitors- SEGA
16. Congenital intracranial mass in a 6-week-old infant. (a)
CT-right frontal mass B. a large vessel supplying the
right frontal mass (c) restricted diffusion.(d) high
vascularity and intense contrast enhancement.
total gross-specimen resection and one session of
chemotherapy. HPE-malignant GBM.Twelve years after
the tumor resection, the patient is alive, with no
evidence of disease recurrence.
infantile HGG generally are
younger than 3 years and
have a favorable prognosis,
given the genetic signature of
this cancer, irrespective of
its radiologic and histologic
phenotypes of malignancy
17.
18.
19.
20. Role of Imaging HGG
• diffusion restriction, irregular and infiltrative margins, and
peritumoral edema may aid
• The pattern and intensity of contrast enhancement observed in
supratentorial gliomas do not necessarily correlate with tumor grade
• Tumor location in the posterior fossa - tumor grade- DIPG -an
expansile mass of the ventral pons.
• The majority of posterior fossa LGGs arise from the tectal plate,
midline dorsal pons, and lateral medulla, with dorsal pontine and
medullary LGGs usually manifesting as exophytic masses
26. WNT SHH GROUP 3 GROUP 4
LOCATION CP angle, along with
lateral recess of
fourth ventricle
Lateral cerebellum Midline Midline
ENHANCEMNT Variable Intence Peripheral/
heterogenous/lepto
meninegeal
Minimal/no
METASTASIS
RECURRENCE
Wont affect the
prognosis
Always surgical site
Early
“sugar
coating,” pattern
Tumour bed with
metastasis
Early
Nodular
Radiation induced
GBM
MRS Non specific Cho,lipid peak,
Low creatine,absent
taurine peak
Tau,creatine peak Tau,creatine peak
27.
28.
29. Treatment Approach
• Surgery, chemo radiation
• Risk stratification according to molecular type
• Avoid radiation in Wnt type, less than 3 years
36. Conclusion
• Pediatric brain tumors do not represent a continuum of adult tumors;
rather, they represent a separate group of neoplasms with distinct
genomic and imaging characteristics
• As the field of radiogenomics is rapidly expanding, radiologists
understanding of tumor genetics is now key and will continue to be so
in the future.
