Low grade glioma

Epidemiology
~20,000 primary brain tumors are diagnosed each year
Peak incidence in 20's and 30's
LGG is more common than HGG
Associated with NF1, tuberous sclerosis

Pathology
Oligodendroglioma: favorable; 1p19q deletion in 60%
Astrocytoma: gemistocytic thought to be more aggressive than fibrillary/protoplasmic types; 1p19q deleted in 10%

Clinical
Headache, seizure*, neurologic deficits*

Prognostic factors (PMID 11956268)
1) Histology: 5Y-OS for pure oligo 70%, mixed OA 56%, pure astro 37%
2) Age: Older than 40 is worse
3) Tumor size: Bigger than 6cm is worse
4) Neurologic deficit: Having one is bad; seizures are a good prognostic factor in the absence of other deficits
5) Tumor crossing midline
6) Tumor enhancement
7) Extent of resection

Surgery
Diagnostic and therapeutic

Radiation
Timing of treatment (EORTC 22845, PMID 16168780): Randomization was to immediate RT vs. deferring RT until tumor progression.  Early RT improved PFS (median 5.3 vs. 3.4 years) but did not affect overall survival (7.4 vs 7.2 years).  Early RT patients also experienced better seizure control.  Rates of conversion to GBM were similar in the two arms.  No prospective QOL analysis was performed.

Dosing (EORTC 22844, PMID 8948338; Intergroup, PMID 11980997): Randomization was 45 vs. 59.4Gy in EORTC trial and 50.4 vs. 64.8Gy in Intergroup trial.  Neither study showed a significant benefit of dose escalation in terms of OS or PFS.  In the Intergroup trial, a higher incidence of radiation necrosis was seen in the high dose arm.

Chemo (RTOG 9802): Patients were randomized to RT 54Gy +/- PCV chemotherapy.  Initially, no improvement in PFS or OS was seen in the PCV group which also experienced higher toxicity. Updated results presented at ASCO 2014 showed a significant overall survival benefit to adjuvant PCV (13.3 vs. 7.8 years). Astrocytoma or mixed oligo/astrocytoma histology was associated with worse survival, as was male sex. Survival analysis based on 1p/19q deletion status is pending.