Tumour Diagnosis and Treatment
How are brain tumours diagnosed? Although we can make educated guesses
when it comes to patients with brain tumours, definitive diagnosis
depends on obtaining tissue. This can only be done through surgery. The
least invasive technique is a needle biopsy performed through a small
hole ("burr hole"). This is sometimes performed under local
anaesthetic. The overall risk of complications occurring from a needle
biopsy is less than 5%.
One important downside to the needle biopsy approach is the size of the
sample of tissue, sometimes resulting in incorrect results. Secondly,
there is the risk of bleeding, especially when the tumour is in an area
rich in blood vessels e.g. the pineal region. Alternatively, the
surgeon can choose to perform a total or subtotal excision of the
tumour through a larger, more invasive, approach called a craniotomy.
The risk is slightly higher but the tissue yield for diagnosis is much
greater.
How does neurosurgery effect the symptoms of a brain tumour?
Palliation
essentially means "making the patient feel better". Some tumours can
cause symptoms of headache and drowsiness because of their large size.
This is called "mass effect". Surgery to reduce the size of the tumour
may relieve these symptoms. Also, reducing the size of the tumour or
completely removing it can sometimes reverse neurological deficits such
as weakness and visual disturbances. Unfortunately, the surgeon is
unable to predict the "reversibility" of the deficits preoperatively,
as some brain tumours invade the normal brain tissue. Alternatively
other brain tumours push the normal tissue aside. A general rule is
that patients who improve with preoperative steroids will likely
improve with surgery.
What can be the down side of 'successful' brain tumour surgery?
It is
important that patients (and their families) consider all the potential
outcomes of surgery before deciding to go ahead.
What is adjuvant therapy?
In patients with cancer, adjuvant therapy
generally refers to the use of chemotherapy and radiotherapy to kill
cancer cells, especially those remaining after surgical removal of the
tumour.
What effect does neurosurgery have on adjuvant therapy?
Younger
patients with aggressive (high grade) gliomas have shown improved
outcomes if most of the tumour cells have already been surgically
removed. This benefit is not as applicable to older patients. Advocates
of surgery say that there may be less chance of malignant
transformation of tumour cells if there are less cells to transform.
Those who are against surgery for low grade gliomas claim that there is
the same chance for malignant transformation if there are 10,000 cells
or 10 million cells. Furthermore, they also fear that surgery may
invoke malignant transformation. It is very important that each patient
is individually assessed.
Why offer surgery before radiotherapy or chemotherapy?
One of the most
commonly accepted principles of oncological (cancer) surgery is a
concept called cytoreduction. This means that chemotherapy and
radiotherapy will have more of a chance of working when the bulk of the
tumour has been reduced. There a few exceptions to this rule e.g.
tumours that are very vascular (contain a lot of blood vessels) may be
more amenable to surgery once their blood supply has been reduced, or
tumours that spread when manipulated may be modified with pre-operative
chemo or radiotherapy so that this doesn't happen at the time of
surgery.
What are the treatment options for low grade gliomas?
This is a
controversial area. Certainly, in children, there is little doubt that
surgery is indicated because of the chance of cure, the
re-establishment of the normal flow of spinal fluid and the improvement
surgery gives to the child's symptoms. Even in adults, surgery can
result in cure, although this is less common. Advocates of surgery say
that there may be less chance of malignant transformation if there are
less cells to transform. Those who are against surgery for low grade
gliomas claim that there is as much chance for malignant transformation
if there are 10,000 cells or 10 million cells. Furthermore, they also
fear that surgery may invoke malignant transformation. For these
reasons, it is very important that patients be assessed individually
before any decision to operate can be made.
Needle Biopsy
What is a needle biopsy? Accurate diagnosis of brain tumors generally
relies upon the analysis of affected brain tissue. The least invasive
technique used to collect a tissue sample from the brain is a needle
biopsy. It is performed through a small hole drilled into the skull
("bur hole"). This is procedure is sometimes performed under local
anaesthetic. The overall risk of complications occurring from a needle
biopsy is less than 5%.
What are the possible problems associated with a needle biopsy? An
important downside to the needle biopsy approach is the small size of
the tissue sample, sometimes resulting in an incorrect diagnosis. There
is also the risk of bleeding, especially when the tumor is in an area
rich in blood vessels e.g. the pineal region.
What is an alternative to a needle biopsy? A neurosurgeon may choose to
perform a total or subtotal excision of the tumour through a larger,
more invasive, approach called a craniotomy. The risk is slightly
higher than a needle biopsy, but the tissue yield for diagnosis is much
greater.
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