2008 Factsheet Medulloblastoma and Primitive Neuroectodermal Tumour (PNET)

Children’s Cancer and Leukaemia Group
2008 Factsheet
Medulloblastoma and Primitive Neuroectodermal Tumour (PNET)
This information sheet is designed to
be used with the accompanying booklet
Brain and Spinal Tumours in Children and
Young People – A Parent’s Guide. You will
find some references to the Guide in this
factsheet. You may also find it helpful to
read the CCLG/Cancerbackup booklet
A Parent’s Guide to Children’s Cancers
which provides more information about
cancers in children, their diagnosis and
treatment and the support services
available. You may also want to discuss the
information with a nurse or doctor involved
in the treatment of your child.
What are Medulloblastoma and PNET?
Medulloblastoma and primitive
neuroectodermal tumour (PNET) are
malignant brain tumours which arise
from nerve cells. They occur mainly in
childhood (usually under the age of 10),
and only occasionally in adults. There are
approximately 80 cases diagnosed each
year in the UK. There is no known cause for
these tumours.
Medulloblastoma develops in the
cerebellum, the part of the brain at the back
of the head (see diagram page 37). This
area of the brain is responsible for balance
and co-ordination.
PNET looks the same as Medulloblastoma
under the microscope but can develop
in any area of the brain other than the
cerebellum. Medulloblastoma is more
common than PNET.
Medulloblastoma and PNET can spread via
the cerebrospinal fluid (CSF) to other parts
of the central nervous system. Spread to
other organs outside of the central nervous
system is rare. These tumours may block
the flow of CSF leading to a condition
called hydrocephalus (see page 8) and so
raise the pressure inside the skull (raised
intracranial pressure).
What are the symptoms of
• Poor balance and coordination caused
by damage to the cerebellum.
• Headache, nausea, vomiting, and
tiredness due to hydrocephalus and
raised intracranial pressure.
• Sight problems:
Squint which may be caused by
hydrocephalus pressing on the nerves
supplying the eye muscles.
Papilloedema (swelling of the optic
nerve) which is caused by raised
intracranial pressure. This can be seen
PAGE 1 OF 3 CCLG Factsheet Medulloblastoma and PNET June 2008
when a doctor looks at the back of the
eye (the retina) with an ophthalmoscope
(a special light used to look through the
pupil to the back of the eye).
What are the symptoms of PNET?
These vary depending on the area of the
brain in which the PNET has developed
(see section on clinical signs and
symptoms of brain tumours page 2).
What is the treatment?
The first step is usually to relieve the
hydrocephalus, if present, and so reduce
the raised intracranial pressure. This may
be achieved by removal of the tumour or
by insertion of a shunt (a drain) to divert
the blocked fluid build up. The next step
in treatment is to remove as much of the
tumour as possible, without damaging
the surrounding brain tissue. However
complete removal is not always possible.
Before the operation to remove the tumour,
a magnetic resonance (MR) scan (see
page 4) of the brain and spine is usually
performed to check whether the tumour
has spread to any other area of the nervous
system. A second scan is performed just
after the operation to find out how much of
the tumour has been removed.
to the whole brain and spine (this is
called craniospinal radiotherapy). This
will also include the whole CSF space
which surrounds the brain and spinal
cord. Craniospinal radiotherapy is one
of the most complex techniques used in
radiotherapy departments and requires
a lot of preparation and planning time.
Radiotherapy is given with the child lying
face down wearing a custom‑made perspex
head mask. These masks are essential
to ensure the head remains perfectly still
during treatment. Radiotherapy treatment
will also involve an extra boost of treatment
to the area from where the original tumour
was removed (the cerebellum in the case of
Chemotherapy has not, in the past, been
used routinely for all children. However,
chemotherapy is now often used for
younger children as part of a clinical trial.
The choice of drugs and how and when
they will be given will be discussed with
you by your consultant and liaison nurse.
As children under 3 years will not receive
craniospinal radiotherapy as standard they
are treated using a chemotherapy only
approach, at least initially. It may then
be necessary to give radiotherapy to the
tumour site only in some cases.
It is rarely possible to remove every cell
of the tumour. Surgery will be followed
by further treatment. Post‑operative
radiotherapy is usually the standard
therapy for children over the age of three
years but may be needed in younger
children if chemotherapy is not successful.
As cells from medulloblastomas or
PNETs can spread via the CSF, it is
essential that radiotherapy is given
What is the outlook?
The aim of treatment is cure and, in
general, medulloblastoma and PNET
respond to treatment. For medulloblastoma
that has not spread to any other area
of the brain or the spinal cord, and has
been completely or nearly completely
removed by the operation, the chance of
cure is good. However, cure can never be
PAGE 2 OF 3 CCLG Factsheet Medulloblastoma and PNET June 2008
Regrettably, for medulloblastomas that
have spread, or for PNET, there is a lower
chance of cure. If the tumour recurs it
may grow back relatively early, i.e. within
the first year or two but can sometimes
grow back more than five years later. If the
tumour comes back after treatment the
chances of curing it are very small.
support link for patients diagnosed with a
brain tumour and their families.
Tel: 0845 130 9733
Website www.braintumourtrust.co.uk
How will my child be followed up?
This will include regular clinic visits and
regular brain scans. It is important that
any problems or symptoms your child
has in between these clinic visits should
be reported as soon as they occur. How
your child is feeling is the most important
aspect of follow‑up and this is just as
important as scans.
Who has produced this information?
This factsheet has been produced by the
Children’s Cancer and Leukaemia Group.
The factsheets and accompanying booklet
Brain and Spinal Tumours in Children
and Young People, A Parent’s Guide have
been sponsored by a donation from the
Samantha Dickson Brain Tumour Trust
Children’s Cancer and Leukaemia
Group (CCLG)
An organisation for professionals
treating children with cancer, including
coordination of clinical trials. The CCLG
provides a range of information for patients
and families affected by childhood cancer.
Tel: 0116 249 4460
Website www.cclg.org.uk
Samantha Dickson Brain Tumour Trust
The Samantha Dickson Brain Tumour Trust
raises funds for research and offers a vital
PAGE 3 OF 3 CCLG Factsheet Medulloblastoma and PNET June 2008