2. Found anywhere
oligodendrocytes are. http://science-naturalphenomena.blogspot.com.au/2009/04/oligodendrocytes.html
Most commonly found
in cerebral hemispheres
Relatively slow growing
Rarely spread outside CNS
Drop mets 1-2% of the time
3. 2 – 5% of all brain tumours
5 – 33% of all Glial tumours
Most common in 30 y.o. – 50 y.o.
Rarely found in children
M:F = 1.1
Only known aetiology, exposure to ioninsing
radiation
4.
5. MRI – in most cases
CT – only if MRI contraindicated
Biopsy
Surgery Insight: the role of surgery in the management of low-grade gliomas Nader Pouratian, fNature Clinical
Practice Neurology (2007) 3, 628-639
6. WHO guidelines rather than TNM
Two tier system
Grade II (77%) (left picture)
Grade III(23%) (right picture)
Grade II tumours can recur as Grade III
tumours
http://oligodendroglioma.org/
http://radiographics.rsna.org/content/25/6/1669/F2.expansion.html
7. Standard treatment approach – surgery
Most often not fully resected
RT alone, RT/Chemo or Chemo alone post
surgery
Watchful waiting
8. Mixed feelings on timing of RT use for
treatment
One EORTC study, 311 patients
Immediate post operative RT
Delayed RT
~8 years later
Immediate RT = increased progression free survival
No effect on overall survival
Consensus, RT given immediately only if rapid
disease progression is indicated
9. Supine, head to gantry
Stabilisation – personalised neck shape and
mask
Localisation – head and neck baseboard
CT or CT/MRI fusion
11. GTV/CTV/PTV and OAR contoured
Conformal, IMRT as needed depending on
tumour location
Beam arrangement – considers OAR
Upwards of three beams, weighting and
wedges as required
45 – 66 Gy, most often 54/30/5
13. Hair loss
Erythema
Fatigue
Change in taste
Xerostima
Headaches
Worsening of seizures
Nausea and vomiting
14. Cognitive impairment
Changes in vision
Stroke-like brain injury
Effects on pituitary function (hormonal
changes)
Secondary cancers
15. Oligodendroglioma patients usually present
with seizures
Like all CNS tumours WHO classification over
TNM staging
Surgery is the best treatment approach
Quite responsive to chemotherapy
RT is not immediate but when patient
becomes symptomatic
Conformal or IMRT treatment
16.
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Editor's Notes
Oligodendrocytes are a type of glial cell found in the central nervous system (CNS) and can be seen in the image at the top right. Oligodendrogliomas are a CNS tumour which can be found anywhere that oligodendrocytes can be found. They are most commonly located in the cerebral hemispheres with 55% of all oligodendrogliomas located in the frontal lobe (Lessman, 1995;Ludwig, 1986). Other common locations include the temporal and parietal lobes (Ludwig, 1986). Only 4%, 3% and 1% are found in the occipital lobe, cerebellum and spinal cord respectively (Ludwig, 1986). Oligodendrogliomas are relatively slow growing (Matthews, 2012) and, whilst it is uncommon for them to spread outside of the CNS, such spread is more common than in other CNS tumours (Van den Bent, 1998; Shah, 1997).It is believed that this is due to the increased survival time of oligodendroglioma patients because of the slow growing nature of these tumours. Drop mets occur only 1 – 2% of the time (Van den Bent, 1998; Shah, 1997).
Oligodendrogliomas are relatively rare accounting for 2 – 5% of brain tumours (Coons, 1997; Paeleologos, 2001; Daumas-Duport, 1997; Greenberg, 1999). It is estimated that oligodendrogliomas repesent 5 – 20% of all glial tumours (Jukich, 2001; Engelhard, 2002). The reason for such a large range is that in recent years the perceived incidence of oligodendrogliomas has increased. This is due to the introduction of MRI’s, which has increased the ability to detect these tumours and is also due to oligodendrogliomas previously being mis-diagnosed as astrocytomas (Jukich, 2001; Engelhard, 2002; Matthews, 2001). Oligodendrogliomas are most commonly found in 30 – 50 year olds and are rarely found in children. They occur almost equally in males and females and have no known aetiology aside from exposure to ionising radiaion.
Oligodendroglioma present in the same manner as for all brain tumours. Symptoms can be generalised, as a result of the overall increased intracranial pressure, or focal, which arise from local pressure due to the growing tumour. The most common presenting symptom of oligodendroglioma is seizures (Lote, 1998). Patients may also develop these later if they don’t initially present with them. Like all other brain tumours oligodendroglioma patients also often present with headaches. These are indicitive of a brain tumour when accompanied by vomiting and nausea. Additionally, if they are worse at night, with change in body positioning eg standing to lying, or worse with coughing/sneezing etc. they can indicate a tumour (Forsyth, 1993). Syncope, a loss of consciousness due to increased intracranial pressure, and Cognitive dysfunction, such as memory problems or mood/personality changes can also occur as symptoms of Oligodendroglioma.
The first step in diagnosing brain tumours is usually an MRI or CT scan. In the case of oligodendroglioma this is usually performed after a patient has presented to the doctor with seizures (Daumas – Duport, 1997; Olson, 2000). Although information from the MRI and/or CT could indicate Oligodendroglioma, imaging is mostly used to detect the location and spatial configuration of the tumour in order to plan for biopsy/surgery. Biopsies, usually by mean of surgical rescetion of the tumour, are the only way to get a definitive diagnosis (Jenkinson, 2006; Megyesi, 2004)
Oligodendrogliomas are not staged using the TNM system but using the WHO guidelines (Louis, 2007). The WHO guidelines classify oligodendrogliomas into two tiers (Louis, 2007). The first tier, grade II tumours, are well differentiated. Their histology generally shows some atypical nuclei and low – moderate mitotic activity (Engelhard, 2002; Reifenberger, 2000). 77% of pure oligodendrogliomas are grade II. Grade three tumours are anaplastic oligodendrogliomas and account for 23% of pure oligodendrogliomas. Grade III oligodendrogliomas have moderate – high mitotic activity, noticable microvascular invasion, as shown by the arrows in the diagram, and necrosis (Engelhard, 2002; Reifenberger, 2000). It is worth noting that grade three tumours can occur initially or “morph” from grade II tumours.
The standard treatment for Oligodendroglioma is surgical excision, with most studies suggesting full resection if possible (Kelles, 2001; Smith, 2008; Shaw, 2008; Hussein, 2002; McGirt, 2008). However, due to the infiltrating nature of this tumour full surgical excision is often not possible (Gannet, 1994; Shaw, 2008; Wallner, 1998). As such post operative Chemotherpy, Radiation therapy, or a combined approach is generally needed. Due to the slow growing nature of oligodendroglimoas studies suggest that radiotherapy treatment should be held off until the patient is symptomatic (Talinsky-Aronov, 2006; Abres, 2006; Karim, 1996). This will be discussed further in the next slide.
There is currently a mixed opinion on the use of RT for Oligodendroglioma. One EORTC study conducted on 311 glioma patients administered immediate post- operative RT to some patients and delayed RT until symptoms appeared in the other patients. Upon reviewing these patients, on average 8 years later, it was found that, whilst giving immediate RT improved the progression free survival (5.4 years compared to 3.7 years for delayed RT) there was no overall survival benefit from the immediate radiation (van den Bent, 2005). Because of this study and many like it most often RT is delayed until symptoms appear. Immeadiate RT is given only in the cases where rapid disease progression is indicated (Cairncross, 2012; Karim, 1996).
Oligodendroglioma treatment is simulated and planned as for any other glioma treatment. Patients are supine and are stabilised using a personalised neck shape and mask of some sort. They are located on the bed using the equipment such as a head and neck baseboard. A CT scan is taken and this is sometimes fused with an MRI to obtain greater tumour delineation.
As with any head and neck cancer there are many organs at risk which need to considered when planning radiation therapy for Oligodendroglioma such as the lenses and spinal cord. Organs at risk vary depending on the tumour location (Barrett, 2009).
Where the tumour was not fully excised a GTV is marked as well as a CTV and these are expanded to obtain the PTV. OAR, which are tumour site dependent, are also contoured. The treatment is then planned, with consideration to tumour loction. Both conformal planning and, where OAR are in close proximity, IMRT should be considered. In either situation beams should be placed so as to avoid dose to OAR and maximise dose to the PTV (Barrett, 2009). Generally there are three or more beamsn, angled to avoid dose to OAR (Barrett, 2009). 54Gy in 30 fractions is a typical dose but can vary.
Patients should be monitored in a daily basis for side effects. Dr’s should be informed in dexamthasone or anti-emitcs are required and the patient is not yet taking them. Image verification should be completed for all treatments. For the highly conformal IMRT plan treatment should be verified with daily kV imaging. Online corrections made and verified, by re-imaging before treatment. For conformal plans, where dose gradients are not as steep, weekly imaging, with offline corrections are adequate to ensure treatment is delivered accurately.
As with any radiation therapy there are many expected side effects for treating oligodendroglioma with RT (Squires, 1989). These are the potential acute side effects, obviously the occurrence of these depends on the tumour site. Some form of hair loss, fatigues and erythema is expected with all patients (Squires, 1989). In some cases the patients seizures actually worsen briefly before becoming increasingly better. Most patients hair will grow back of its own accord but, should it not, wigs and other hair accessories can be suggested. Erythema should be managed with good skin care in consultation with the nursing staff. Oral symptoms can be managed with products such as biotene and nausea and vomitting can be managed with antiemetics.
There are also late effects from RT for Oligodendroglioma such as Cognitive impairment Changes in vision Stroke-like brain injury Effects on pituitary function (hormonal changes) Secondary cancers (Olsson, 2000; Duffey, 1996; Desai, 2006).
Oligodendroglioma patients usually present with seizures Like all CNS tumours WHO classification over TNM staging Surgery is the best treatment approach Quite responsive to chemotherapy RT is not immediate but when patient becomes symptomatic Conformal or IMRT treatment