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Radiation Oncology Residency > Low-Grade Glioma > Flashcards

Low-Grade Glioma Flashcards

1
Q

Low-grade gliomas (LGGs) account for what % of all primary brain tumors?

A

∼10% of all primary brain tumors are LGGs.

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2
Q

Is there a racial predilection for LGG?

A

Yes. Whites are more commonly affected than blacks (2:1).

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3
Q

What are the histologic subtypes of LGGs?

A

Histologic subtypes of LGG (WHO 2016 update):
Grade I: pilocytic astrocytoma, subependymal giant cell tumor
Grade II: diffuse astrocytoma (fibrillary, protoplasmic, gemistocytic) including isocitrate dehydrogenase (IDH) mutant/wildtype; oligodendroglioma, IDH mutant/1p19q co-deleted; and oligoastrocytoma

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4
Q

What 4 pathologic features determine glioma grading?

A 
Necrosis
Atypia
Mitotic figures
Endothelial proliferation
(Mnemonic: NAME or AMEN)
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5
Q

Which subtype of diffuse astrocytoma has the worst prognosis?

A

The gemistocytic subtype tends to de-differentiate and has the worst prognosis. Some prefer to treat it like a high grade glioma.

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6
Q

Where anatomically does pilocytic astrocytoma most commonly present?

A

Most commonly presents in the PF (80% cerebellar, 20% supratentorial).

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7
Q

What pathologic feature is characteristic of pilocytic astrocytoma?

A

Rosenthal fibers are characteristic of pilocytic astrocytoma.

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8
Q

Where do grade II LGGs most commonly present?

A

Grade II LGGs most commonly present in the supratentorium.

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9
Q

What is the median age of Dx for pilocytic astrocytoma vs. other LGG?

A

The median age for pilocytic astrocytoma is 10–20 yrs and for grade II LGG is 30–40 yrs.

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10
Q

What genetic changes are important prognostic factors in LGG?

A

In LGG, LOH 1p19q and IDH mutations portend a better survival. p53 mutation indicates poorer survival and time to malignant transformation.
IDH1 and IDH2 mutations are strongly associated with better prognosis.

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11
Q

What genetic change is prognostic in oligodendroglioma?

A

LOH 1p19q is prognostic in oligodendroglioma and is present in over 50% of cases. Associated with sup OS (MS 10 yrs in del 1p/19q vs. 3 yrs in intact)
and PFS. (Jenkins RB et al., Cancer Res 2006)

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12
Q

What is the characteristic pathologic appearance of oligodendroglioma?

A

“Fried egg” appearance (round cells with nuclear halo) is characteristic of oligodendroglioma.

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13
Q

Where do most oligodendrogliomas occur in the brain?

A

Most oligodendrogliomas occur in the hemispheres (80%).

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14
Q

Anaplastic transformation from LGG to HGG occurs in what % of pts?

A

∼70%–80% of pts with LGG will undergo anaplastic transformation (based on EORTC 22845).

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15
Q

What chromosome is affected in NF-1, and with what type of gliomas is it associated?

A

NF-1 is a result of a mutation on the long arm of chromosome 17 (NF1/neurofibromin tumor suppressor gene) and is associated with optic/intracranial gliomas

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16
Q

What chromosome is affected in tuberous sclerosis, and with what glioma is it associated?

A

Tuberous sclerosis is a result of a mutation on chromosome 9 (TSC1 tumor suppressor gene) or chromosome 16 (TSC2 tumor suppressor gene)and is
associated with subependymal giant cell astrocytoma.

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17
Q

What syndrome is associated with gliomas and GI polyposis?

A

Turcot syndrome is associated with gliomas and polyposis.

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18
Q

With what Sx do LGGs most commonly present?

A

Seizures (60%–70%, better prognosis) > HA, focal neurologic Sx

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19
Q

What is the 5-yr OS of LGG?

A

The 5-yr OS is 60%–70%.

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20
Q

What is the workup for suspected glioma?

A

Suspected glioma workup: H&P, basic labs, and MRI brain

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21
Q

How should tissue be acquired for Dx?

A

Tissue should be acquired by max safe resection (per the NCCN), otherwise by stereotactic Bx.

22
Q

What is the typical MRI characteristic seen in LGG?

A

On MRI, LGGs appear hypointense on T1, are nonenhancing with gadolinium, and show T2 prolongation.

23
Q

What is the typical MRI appearance of pilocytic astrocytoma?

A

Well-circumscribed, cystic mass, intensely enhancing solid mural nodule

24
Q

What % of nonenhancing lesions are grade III gliomas?

A

∼30% are grade III gliomas (65% are LGG).

25
Q

What feature has been associated with oligodendrogliomas on imaging?

A

Calcifications are a prominent feature on imaging of oligodendrogliomas

26
Q

What is suggestive of a malignant tumor on MR spectroscopy?

A

Increased choline (cell membrane marker), low creatine (energy metabolite), and low N-acetyl-aspartate (a neuronal marker) are suggestive of malignancy on MR spectroscopy.

27
Q

What is the staging of LGG?

A

There is no formal staging for LGG.

28
Q

What are the 5 negative prognostic factors for LGG as determined by EORTC 22844 and 22845?

A 
Negative prognostic factors per the EORTC index:
1. Age >40 yrs
2. Astrocytoma histology
3. Tumors ≥6 cm
4. Tumors crossing midline
5. Preop neurologic deficits
(Pignatti F et al., JCO 2002)
29
Q

What is the general Tx paradigm used for LGGs?

A

LGG Tx paradigm: max safe resection → observation if low risk (≤40 yo and GTR) or adj RT +/– PCV chemo if high risk (>40 yo or STR).

30
Q

What prospective data support initial observation over adj RT in LGG (early vs. delayed)?

A 
EORTC 22845 (“Non-Believers Trial”) randomized 314 LGG pts to early RT vs. delayed RT until time of progression. Concluded early RT lengthens
PFS (5.3 yrs vs. 3.4 yrs) and seizure control (25% vs. 41%) but does not impact OS. (Van den Bent MJ et al., Lancet 2005)
31
Q

What adj and salvage chemo regimens are typically used in LGG?

A

Chemo agents used in LGG:

  1. TMZ
  2. BCNU/CCNU (carmustine/lomustine)
  3. PCV (procarbazine/CCNU/vincristine)
32
Q

What RT dose is typically used for LGG?

A

LGG is commonly treated to 50.4–54 Gy (1.8 Gy/fx)

33
Q

A complete resection can be achieved in what proportion of pts with LGGs?

A

Appx one-third of pts with LGGs have a GTR.

34
Q

Within what timeframe should postop MRI be obtained for pts with LGGs? Why is it needed?

A

Postop MRI should be done within 48–72 hrs of Sg to assess for residual Dz/extent of resection.

35
Q

In LGG, how are the RT Tx volumes defined, and what margins are typically used?

A

Per RTOG1072/ECOG E3F05:
GTV = cavity + T2/FLAIR + enhancement
CTV = GTV + 1 cm
PTV = CTV + 0.5 cm

36
Q

In what clinical circumstances can adj RT be considered for LGGs?

A
  1. For pts >40 yo or with STR per RTOG 9802
  2. For pts with 3 of 5 high-risk features per the EORTC index (above).
    No LOH 1p19q or IDH mutation are also adverse features that may be considered.
37
Q

What % of LGG pts undergoing initial observation in EORTC 22845 eventually required salvage RT?

A

In EORTC 22845, 65% of pts in the observation arm rcvd subsequent salvage RT.

38
Q

What proportion of pts do not need salvage RT when observed after surgical resection for LGG?

A

Per EORTC 22845, appx one-third of pts will not require salvage RT.

39
Q

In EORTC 22845, how did the OS after progression compare in the adj vs. observation arms?

A

Survival after progression was better in initially observed pts, most of whom rcvd salvage RT. OS after 1st recurrence was 3.4 yrs vs. 1 yr (SS).

40
Q

Is there prospective evidence to support dose escalation with adj RT for LGG?

A

No. Dose escalation in LGG has been evaluated in 2 RCTs, neither of which showed a benefit:

  1. EORTC 22844 randomized 343 pts to adj RT 45 Gy vs. 59.4 Gy. There was no difference in 5-yr OS (58%–59%) or PFS (47%–50%). (Karim AB et al., IJROBP 1996)
  2. INT/NCCTG randomized 203 pts to adj RT 50.4 Gy vs. 64.8 Gy. There was no difference in 5-yr OS (65%–72%). 92% of failures were in-field. (Shaw EG et al., JCO 2002)
41
Q

Is adj therapy needed after GTR or STR for pilocytic astrocytoma in adults?

A

No. Brown et al. prospectively followed 20 young (<47 yo) adult pilocytic astrocytoma pts s/p GTR, STR (6 pts), or Bx (3 pts). 20-yr OS and PFS in GTR pts was 100%. 20-yr OS and PFS for STR was 100% and 83%.
(Neurooncol Pract 2015)

42
Q

Is there a benefit of chemo with RT for LGGs with high-risk features?

A

RTOG 9802 stratified pts into low risk (age <40 yrs s/p GTR) and high risk (age >40 yrs or STR/Bx only). High-risk pts were randomized to adj RT alone (54 Gy) vs. RT + PCV. Outcomes were better in the chemo arm and were SS after long-term f/u (10-yr OS: 40% vs. 60%; PFS: 21% vs. 51%). Benefit to actuarial PFS and OS were apparent after 2 and 4 yrs, respectively. (Buckner et al., NEJM 2016)

43
Q

In RTOG 9802, what were the 5-yr OS and PFS for low-risk pts observed after GTR?

A

In RTOG 9802, low-risk pts (<40 yo s/p GTR) were observed and had 5-yr OS of 93% and PFS of 48%. (Shaw et al., J Neurosurg 2008)

44
Q

Is there a role for TMZ in the initial Tx of LGG?

A

Results of 2 trials are preliminary:
1. Intergroup EORTC 22033–26033 randomized 477 high-risk LGG pts (>1 of: age >40, progressive Dz, tumor ≥5 cm, tumor crossing midline, neurologic Sx) to adj RT vs. adj TMZ. Overall there was no difference in
PFS or OS at 4 yrs. In exploratory analyses, pts with IDH mutations/1p19q noncodel had better PFS with RT compared to TMZ. IDH-wt and IDHmt/codel pts saw no PFS difference b/t the 2 arms. (Baumert BG et al.,
Lancet Oncol 2016)
2. RTOG 0424 is a phase II study that enrolled high-risk LGG pts (3 of 5 EORTC features) and treated with RT (54 Gy) + concurrent TMZ then adj TMZ. Preliminary results show a 3-yr OS rate of 73%, which is higher than
historic controls. The 3-yr PFS was 59.2%, however, 43% of pts had G3 adverse events. (Fisher BJ et al., IJROBP 2015)

45
Q

For pilocytic astrocytoma, what is the estimated 10-yr and 20-yr RFS in pts treated with GTR alone?

A

10-yr and 20-yr RFS is 100% in pilocytic astrocytoma pts treated with GTR alone. (Brown et al., Neurooncol Pract 2015)

46
Q

In pts with oligodendroglioma/mixed oligodendroglioma, what is the median OS for those +/- LOH for 1p19q?

A

With LOH 1p19q: median OS ∼13 yrs

Without LOH 1p19p: median OS ∼9 yrs

47
Q

How does RT affect QOL in the Tx of LGG?

A

QOL in LGG is impacted by Sg, RT, chemo, and seizure meds. Based on the EORTC 22844 dose-escalation study, higher-dose RT was significantly associated with fatigue/malaise and insomnia and ↓ emotional functioning.
(Kiebert GM et al., Eur J Cancer 1998)

48
Q

Does RT predispose LGG lesions to malignant transformation?

A

No. RT is not associated with an ↑ rate of malignant transformation. In EORTC 22845, there was a 70% transformation rate in both the adj and observation arms.

49
Q

What is the NCCN recommended radiographic surveillance frequency for LGG post Tx?

A

The recommended imaging frequency post Tx is MRI q3–6mos for 1st 5 yrs, then annually. (NCCN 2018)

50
Q

What is the constraint for the optic chiasm in conventional fractionation vs. single fraction SRS?

A

Chiasm is commonly constrained to 54 Gy in

1.8–2 Gy/fx and 8 Gy in a single fx.

51
Q

What is the cause of somnolence syndrome after brain RT?

A

Somnolence syndrome is thought to be caused by demyelination.

Radiation Oncology Residency (44 decks)

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