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Pedes > Medulloblastoma > Flashcards

Medulloblastoma Flashcards

1
Q

What percetage of pts have CSF dissemination at Dx

A

33%

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2
Q

Peak ages for group C

A

4-6 yrs

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3
Q

Peak ages for SHH

A

25 ys

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4
Q

What % are familial and what are the disorders

A

Turcot and Gorlin
2-5%

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5
Q

What is the workup for medulloblastoma

A

-H&P including neurological exam, fundoscopic exam
-Imaging: MRI of brain and spine
-If very symptomatic, best to go straight to surgery with placement of posteror fossa drain (not shunt)
-Do not obtain CSF cytology before surgery due to risk of herniation
-MRI of brain 24-72 hrs post surgery
-Obtain CSF cytology 10-14 days after surgery to avoid false positives
Other imaging: CT CAP
Labs: CBC, CMP
Bone marrow biopsy as indicated for adults
Baseline audiometry, neurocognitive/IQ testing, growth measurements, neuroendocrine, and ophthalmology

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6
Q

What are infatentorial/posterior fossa tumors

A

medulloblastoma, ATRT, mets, ependymoma, JCA

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7
Q

Differential dx for small round blue cell tumors

A

LEARN NMR
lymphoma
ependymoma
ALL
rhabdomyosarcoma
Neuroblastoma
Neuroepilioma
medulloblastoma
retinoblastoma

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8
Q

What is a characteristic histopatholoigc factor seen in 40% medulloblastoma

A

Home Wright Rosettes
( These are also seen in pineoblastoma, neuroblastoma, PNET)

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9
Q

What is a characteristic genetic factor seen in 50% medulloblastoma

A

17q deletion in 50%

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10
Q

What are the genetic subgroups of medulloblastoma

A

WNT
SHH
Group 3
Group 4

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11
Q

Describe the WNT subgroup

A

18% of patients
CTNNB1 mutation
Best prognosis
Not seen in infants
18Gy CSI on new protocol

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12
Q

Describe SHH subgroup

A

19% of patients
PTCH1 (Gorlin), MYCN mutation
Usually desmoplastic
Occur laterally
Most common in children and adults

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13
Q

Describe Group 3

A

Myc amplified
Worse prognosis
Typically occurs before puberty
Distant mets at diagnosis are common

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14
Q

Describe group 4

A

CDK6 , MYCN amplification
adolesence

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15
Q

Describe the M staging for medulloblastoma

A

M0- no mets
M1- + CSF
M2- intracranial nodules
M3- spinal nodules (M3a spine only, M3b spine and brain nodules)
M4- mets outside CSF

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16
Q

What is standard risk medulloblastoma?

A

> 3yrs
GTR or <1.5 cm residual disease
Classic or desmoplastic histology

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17
Q

What is intermediate risk medulloblastoma

A

> 3 yrs
GTR or <1.5 cm residual disease
but with large cell or anaplastic histology

18
Q

What is high risk medulloblastoma

A

< 3 yrs
> 1.5 cm residual disease
Diffuse anaplasia
M+
PNET

19
Q

What is the treatment paradigm for <3 yrs vs. > 3 years medulloblastoma

A

> 3yo: Maximal safe surgical resection followed by concurrent chemoRT within 31 days post-op then Adjuvant chemo

<3yo: Maximal safe surgical resection followed by chemotherapy alone. RT for salvage.

20
Q

What is the most important predictor of survival in medulloblastoma patients

A

extent of surgery

21
Q

What chemotherapy is used in kids <3 yrs who cannot receive chemotherapy

A

cyclophosphamide/vincristine
carboplatin/etoposide

22
Q

Should standard risk adults get chemo

A

No

23
Q

What chemo is used for concurrent chemoRT

A

Vincristine

24
Q

What labs are needed for starting CSI in medulloblastoma and what should be done if these heme values are not met?

A

ANC>1000
platlets>100K

If these lab values are not met, then do boost fields first, and do spine fields after

25
Q

Describe sim set up

A

-can be prone or supine
aquaplast mask for immobilization
-chin extended to avoid divergence through the oral cavity
-shoulders pulled down as much as possible
-scan vertex through mid femur

for patients 0-4 years- opposed laterals for brain and matched electron fields for spine

26
Q

What is the benefit of using protons

A

proton CSI can improve conformality to high dose regions and reduce risk of secondary malignancy and dose to heart, esophagus, stomach, bowel etc.

27
Q

Describe 3D CSI Script

A

-Prone positioning, extend the neck to avoid divergence of spinal fields into oral cavity
-Arms at sides with shoulders relaxed to allow lowest possible edge of spinal fields
 Set the spine field first for the collimator angle to match divergence
* Superior = C4-7, or as low as possible without going through the shoulders.
* Inferior = thecal sac (S2-3) + 1-2cm margin inferiorly
* Lateral = 1cm lateral to transverse process, spade at sacrum to include SI joints
* Use a single field if length <40cm

28
Q

What should be done if the spine measured over 35 cm

A

Treat at 120cm SSD – increased divergence to tissue, increased scatter, higher Mus,
higher PDD, and greater penumbra results in higher mean doses to all anterior normal
structures

Use two fields – match distal to the cord with the skin gap equation. Consider moving
the gap if this is over gross disease.
Gap S = (0.5)(d)(L1/SSD1 + L2/SSD2)

29
Q

What must be done to reduce hot and cold spots if using 2 fields

A

feathering the junction over 5-7 treatments (once/week)

30
Q

What should be done to reduce the superior divergance of the spine fields

A

rotate the collimator of the cranial fields to match the superior divergance of the spine fields

31
Q

What should be done to minimize the inferiror divergance of the cranial fields

A

Kick the couch towards the gantry (usually 7-10 degrees)

32
Q

Describe the radiation regiment for standard risk patients

A

CSI 23.4Gy —>involved field (IF) boost 54Gy + concurrent weekly vincristine

**Adjuvant chemo **(cisplatin, vincristine, cyclophosphamide or CCNU are all options)
* CTV5040 = preop tumor + bed + 1.0-1.5cm, anatomically constrained, allowing 2mm into brainstem unless involved

33
Q

Describe the radiation for intermediate risk patients

A

CSI 23.4Gy

  • CTV5040 = preop tumor + bed + 1.0-1.5cm, anatomically constrained, allowing 2mm into brainstem unless involved
  • Involved field (IF) boost 54Gy + concurrent weekly vincristine

( Consider adding carboplatin in these patients)

34
Q

Describe treatment of high risk patients

A

CSI 36Gy  posterior fossa (PF) boost 54Gy + concurrent weekly vincristine +/-
carboplatin followed by adjuvant cisplatin-based chemo

35
Q

What should you boost M2 (intracranial mets to)

A

intracranial metastases boosted to 55.8Gy

36
Q

What should you boost M3 (intracranial mets to)

A

spinal metastases above cord boosted to 45Gy, below cord to 50.4Gy

37
Q

M4 diffuse LMD?

A

CSI to 39.6Gy

38
Q

What are the borders of a posterior fossa boost

A

Superior = tentorium
Inferior = C2-3 junction, through foramen magnum
Lateral = bony walls of occiput and temporal bones
Anterior = posterior clinoids and anterior C1, block pituitary unless involved
Posterior = cerebellar fossa/internal occipital protuberance

39
Q

Describe posterior fossa syndrome

A

Occurs in 25% of patients within 1-2 days after surgery
o SAME-R = swallowing difficulties, truncal ataxia, mutism, emotional lability, respiratory failure, gaze
palsy
o Do not delay radiation – typically improves over 1-6 months, but dysarthric speech and ataxia may
remain

40
Q

Describe side effects after CSI

A

o Short seated stature
o Alopecia
o Endocrinopathy, infertility, sterility
o Intellectual/IQ decline:
 Post-surgical complications are a significant contributor to decline in IQ
 Protons have less IQ decline than photons because of conformality of boost volume (boost
volume in posterior fossa does not leak into supratentorial brain)
 Young age at RT, especially <3yo, associated with severe IQ decline

41
Q

Describe outcomes in pediatricts and adults with medduloblastoma

A

Pediatrics:
o Standard risk 5-yr EFS = 80%; 5-yr OS = 80%
o High risk 5-yr EFS = 65%
- Adults:
o 5-yr PFS: 72%
o 5-yr OS: 75%

Pedes (6 decks)

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