1. What is Retinoblastoma?
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Retinoblastoma is a malignant tumour or cancer that develops in
the cells of the eye. More than nine out of ten children with retinoblastoma
can be successfully treated and it has one of the best cure rates
of all children's cancers. In about two thirds of children only
one eye is affected, but in one third tumours develop in both eyes.
When only one eye is affected this is known as unilateral retinoblastoma,
and when both eyes are affected it is called bilateral retinoblastoma.
In very young children who have only one eye affected at diagnosis,
it is possible for a tumour to develop in the second eye several
weeks or even months after the diagnosis of retinoblastoma in the
first eye. The number of tumours found in the eye also varies; sometimes
only one tumour develops at the back of the eye, but not infrequently
there are several tumours, and these may require more than one type
of treatment.
2. How common is
Retinoblastoma?
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Retinoblastoma is one of the less common cancers of childhood and
accounts for only about 3 out of every 100 cancers occurring in
children under the age of 15 years. In the United Kingdom between
40 and 50 children develop this tumour each year. The tumour usually
develops before the age of 5 years and some children are born with
retinoblastoma. Children with bilateral disease tend to present
during the first year of life, whilst the peak age of diagnosis
for children with unilateral disease is between 24 and 30 months.
Less than 5% of cases are diagnosed after the age of 5 years.
3. What causes Retinoblastoma?
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Retinoblastoma occurs in two forms: a genetic, inheritable variant
and a non-genetic, non-inheritable form. Approximately 40% of children
with retinoblastoma have the genetic form of the disease (click
here to link to genetic counselling). In these children, we know
that something goes wrong with a small piece of the genetic material
on chromosome 13. Chromosomes control the way cells grow and develop,
and when a portion of the chromosome is either missing or altered
in some way, various abnormalities may occur and in some cases,
a cancer may develop. Although in a proportion of children with
the genetic form of retinoblastoma the defective gene is inherited
from one of the parents, in the majority of cases we do not know
what causes the abnormal gene to develop. Many people are frightened
that cancer is infectious but there is absolutely no evidence that
you can "catch" retinoblastoma and you should reassure
your friends on this account.
4. Signs and symptoms
of Retinoblastoma.
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The two common signs of retinoblastoma are firstly, an abnormal
appearance of the pupil which tends to reflect light as a white
reflex, like a cat's eye, and secondly, a squint. Less commonly
parents may notice deterioration in their child's vision, or the
eye may become red and inflamed. Pain is an uncommon symptom. Apart
from the eye problem, the majority of children are otherwise well.
However, small proportions of children are referred to their local
paediatrician because of failure to thrive or delayed development.
In these children a chromosome test may reveal an abnormal chromosome
13 and lead to an unsuspected diagnosis of retinoblastoma.
RETINOBLASTOMA occurs in early childhood and affects about 1 child
in 20,000. The tumor develops from the immature retina - the part
of the eye responsible for detecting light and color. There are
both hereditary and non-hereditary forms of retinoblastoma.
In the hereditary form, multiple tumors are found in both eyes,
while in the non-hereditary form only one eye is affected and by
only one tumor.
In the hereditary form, a gene called Rb is lost from chromosome
13. Since the absence of Rb seemed to be linked to retinoblastoma,
it has been suggested that the role of Rb in normal cells is to
suppress tumor formation. Rb is found in all cells of the body,
where under normal conditions it acts as a brake on the cell division
cycle by preventing certain regulatory proteins from triggering
DNA replication. If Rb is missing, a cell can replicate itself
over and over in an uncontrolled manner, resulting in tumor formation.
Untreated, retinoblastoma is almost uniformly fatal, but with
early diagnosis and modern methods of treatment the survival rate
is over 90%. Since the Rb gene is found in all cell types, studying
the molecular mechanism of tumor suppression by Rb will give insight
into the progression of many types of cancer, not just retinoblastoma.
Retinoblastoma treatment requires the cooperation of an ophthalmic
oncologist, pediatric oncologist, and radiation therapist. Over
the last 30 years, treatment has evolved from simple enucleation
(removal of the eye), to eye-sparing radiotherapy, and more recently
to chemotherapy-based multimodality therapy. Though retinoblastomas
are usually cured by radiation, investigators have suggested that
irradiation increases the risk of developing second cancers later
in life.
Several experimental protocols are currently being evaluated to
use chemotherapy to shrink the retinoblastomas in order to treat
them with laser therapy, freezing therapy, and local "plaque"
radiotherapy. Where applicable, these techniques are thought to
be safer than radiation. There is little long-term data on the
safety of this type of multi-modality chemotherapy.
Treatment of retinoblastoma requires a team of doctors made up
of ophthalmic, radiation and pediatric oncologists. Doctors who
are able to evaluate your child, discuss all the different forms
of treatment, and make them available.
