Low Grade Glioma

astrocytomas_mayo.jpg (14059 bytes)

Low Grade Gliomas

Start with this review article (go here or here and see the NCCN site here). The grade and histology are critical in determining the treatment and prognosis for primary brain tumors. Low grade gliomas (grade 1 and 2) are more slow growing and are often treated with surgery.

The role of postOp radiation is somewhat controversial and is discussed below (see CancerNet, and the NCCN guidelines flow chart and the NCCN manuscript,) The treatment of high grade gliomas ( grade 3 anaplastic astrocytoma or grade 4 glioblastoma) are discussed elsewhere.

(Low grade gliomas have a different appearance on MRI or CT compared to glioblastoma see here, here, here, here and here).

Survival tables are noted below. Old age has a negative impact on survival with low grade gliomas. In a large series from the Mayo clinic with patients over 55y the median survival was only 2.7 years (31%/5y and 19%/10y). Other Prognostic factors that affect survival are noted here, age and survival here, grade and survival go here, and the other studies below.

Studies using radiation (go here). Generally if radiation is used the dose is 54Gy in 30 factions as noted in the NCCN guidelines or the RTOG protocol below. The role of radiosurgery in this disease is controversial go here and here

Picture of a low grade glioma before after radiation go here. For more pictures of MRI images go here and here.

In the ongoing RTOG98-02 trial for low grade gliomas has three arms: an observation arm for favorable (age < 40 and gross total resection) and two arms for high risk (subtotal resection/biopsy and/or age > 40y) that include postOp radiation alone versus radiation followed by chemotherapy (6 cycles of PCV Chemotherapy - Procarbazine/CCNU/Vincristine). The radiation dose/technique is as follows:

The target volume is based on the T2 weighted images from the postoperative MRI scan (the preoperative MRI scan can be used in patients who underwent biopsy only) and will include any T2 abnormality suspected of containing tumor plus a 2 cm margin (to block edge). If the tumor has been completely resected, the target volume will be the surgical defect and any T2 abnormality surrounding the surgical defect plus a 2 cm margin (to block edge). There will be no boost volume. The margin may be reduced to a 1 cm margin (to block edge) around critical structures and/or natural barriers to tumor growth (e.g. skull and tentorium). Treatment will be given in 1.8 Gy fractions (to isocenter), 1 fraction per day, 5 days per week and must begin within four weeks after randomization. The total dose will be 54 Gy in 30 fractions over approximately 6 weeks. The target volume must receive 95-105% of the prescribed total dose to be per protocol (encompassed by the 51.3 to 56.7 Gy isodose line).

**Survival by Histology** **(data from RTOG 98-02)**
Survival	Astrocytoma	Astr-oligo	Oligodendroglioma
median	4.7y	7.1y	9.8y
surv/5y	46%	63%	73%
surv/10y	17%	33%	49%

**Survival by Age for Low Grade Gliomas**
Author	Age	Median Survival
Eyre	< 30y	not reached
	30 - 49y	5.5 years
	50 +y	1.6 years
Medberry	<40	6.75 years
	40+y	1.0 years
Piepmeier	< 40y	8.7 years
	40 + y	4.9 years
Shaw	< 35.5y	6.3 years
	35.5y +	4.2 years

**Median Survival by Age** *Groups* (4 series from RTOG)
Survival (age less than)	Survival (age older than)
6.75y (< 40y)	1.0y (> 40y)
8.7y (< 40y)	4.9y (>40y)
6.3y (< 35y)	4.2y (> 35y)
5.5y (< 35y)	1.6y (> 35y)

**5y Survival by Extent of Surgery** **(3 series from RTOG)**
gross total resection	subtotal resection	biopsy only
88%	57%
85%	64%	43%
80%	50%	45%