Retinoblastoma
What is retinoblastoma?
Retinoblastoma is a rare cancer of the retina. The retina is the innermost
layer of the eye, located at the back of the eye, that receives light and images
necessary for vision. About 250 children in the US are diagnosed with this type
of cancer each year. It mostly occurs in children under the age of 5; the
highest incidence of the disease occurs between infancy and age 2. Both males
and females are affected equally. Retinoblastoma can occur in either eye,
however, in about 25 percent of the cases, the tumor is present in both eyes.
Retinoblastoma cells can, in rare cases, spread (metastasize) to other areas of
the body, including the bone marrow.
What causes retinoblastoma?
Retinoblastoma occurs due to mutations in a tumor suppressor gene (called
RB1) located on chromosome #13. Two mutations (or gene changes) are necessary to
"knock-out" this gene, and cause uncontrolled cell growth. In inherited
retinoblastoma (40 percent of the cases), the first mutation is inherited from a
parent, while the second occurs during the development of the retina. In
sporadic retinoblastoma (60 percent of the cases), both mutations occur during
development of the retina. Sporadic means "occurs by chance." Alterations in the
RB1 gene have also been found in other tumors, including osteosarcoma and breast
cancer.
Most children with inherited retinoblastoma generally have tumors
involving both eyes. (In fact, all cases involving both eyes should be
considered hereditary). The RB1 gene is an autosomal dominant gene, which means that
both males and females are equally affected, and there is a 50/50 chance, with
each pregnancy, for a parent to transmit the gene to a child. When a child
inherits the gene, there is about a 90 percent chance for the second mutation to occur,
resulting in retinoblastoma. This means that some children who inherit the
mutation may never get the second mutation, and may, therefore, never develop
retinoblastoma. (They can still transmit the gene to their offspring, however,
so that their children could develop the disease.)
Consider the following statistics:
- Sixty to 75% of retinoblastoma cases involve one eye
(unilateral). Of
these, about 15
percent are inherited, and the remaining 60 percent
are sporadic.
- Approximately 25 percent of retinoblastoma cases are bilateral (both eyes) and hereditary.
- Fifteen percent of retinoblastoma cases
are unilateral (one eye) and hereditary.
Any individual with a positive family history of retinoblastoma may want to
seek genetic counseling to identify the specific risks of passing the gene or
disease to their children.
What are the symptoms of retinoblastoma?
The following are the most common symptoms of retinoblastoma. However, each
child may experience symptoms differently. Symptoms may include:
- leukocoria — a white light reflex that occurs at certain angles when light
is shown into the pupil.
- strabismus (Also called wandering eye or crossed-eyes.) — a misalignment
of the eyes; when one or both eyes do not appear to be "looking" in the same
direction.
- pain or redness around the eye(s).
Often the symptoms may not appear if the disease is diagnosed early. The
symptoms of retinoblastoma may resemble other conditions or medical problems.
Always consult your child's physician for a diagnosis.
How is retinoblastoma diagnosed?
In addition to a complete medical and physical examination, diagnostic
procedures for retinoblastoma may include:
- complete eye examination
- fundoscopic examination — the pupils are dilated so the entire retina can
be viewed and examined.
- computed tomography scan (Also called a CT or CAT scan.) — a diagnostic
imaging procedure that uses a combination of x-rays and computer technology to
produce cross-sectional images (often called slices), both horizontally and
vertically, of the body. A CT scan shows detailed images of any part of the
body, including the bones, muscles, fat, and organs. CT scans are more
detailed than general x-rays.
- magnetic resonance imaging (MRI) — a diagnostic procedure that uses a
combination of large magnets, radiofrequencies, and a computer to produce
detailed images of organs and structures within the body.
- blood tests
- genetic and/or DNA testing
A diagnosis may be made before symptoms are present. If a family history is
positive for retinoblastoma, frequent eye examinations may be necessary at many
stages of the child's development to determine the presence of any tumor. When
retinoblastoma is diagnosed, tests will be performed to determine the size,
number, location of the tumors, and if the tumors have spread to the other parts
of the body. This is called staging and is an important step toward planning a
treatment program.
What are the stages of retinoblastoma?
The Reese-Ellsworth stages of retinoblastoma include:
- Group I — either one or more tumors that are less than 4 disc diameters
(DD) in size and located at or behind the equator.*
- Group II — either one or more tumors that are 4 to 10 DD in size located
at or behind the equator.
- Group III — any lesion in front of the equator or any tumor(s) larger than
10 DD.
- Group IV — multiple tumors with some or all greater than 10 DD in size or
any lesions that extend beyond the back of the eye.
- Group V — very large tumors involving more than half of the retina and
have spread to other sites in the body.
*The "equator" is an imaginary line that divides the eye into two equal parts
There are other staging systems for retinoblastoma. You will need to discuss
this with your child's physician.
Treatment for retinoblastoma:
Specific treatment for retinoblastoma will be determined by your child's
physician based on:
- Your child's age, health and medical history
- Extent of the disease
- Your child's tolerance for specific medications, procedures, or therapies
- Expectations for the course of the disease
- Your opinion or preference
The primary goal of treatment is to remove the tumor and
prevent metastasis (spreading) of the cancer to other parts of the body.
Treatment may include one or more of the following:
- Surgery
- Enucleation (removal of part or all of the eye or eyes involved with the
tumor)
- Chemotherapy
- Radiation therapy
- Laser therapy or photocoagulation
- Thermal therapy
Additional treatment may include one or more of the following:
- Fitting and training for a prosthesis
- Blind or decreased vision adaptation training
- Supportive care (for the side effects of treatment)
- Antibiotics (to prevent/treat infection)
Long-term outlook for a child with retinoblastoma:
Prognosis greatly depends on:
- The extent of the disease
- The size and location of the tumor
- Presence or absence of metastasis
- The tumor's response to therapy
- The age and overall health of your child
- Your child's tolerance of specific medications, procedures, or therapies
- New developments in treatment
As with any cancer, prognosis and long-term survival can vary greatly from
child to child. Every child is unique and treatment and prognosis is structured
around the child's needs. Prompt medical attention and aggressive therapy are
important for the best prognosis.
Continuous follow-up care is essential for a child diagnosed with retinoblastoma. Secondary
cancers have a high incidence among survivors of retinoblastoma. These
secondary cancers are not a relapse or recurrent retinoblastoma, but
are primary tumors (brand new tumors) of other organs. The most common
secondary cancer is osteosarcoma (cancer of the bone). However, retinoblastoma has
been linked to melanoma, breast, lung, bladder and other types of
cancers much later in life. The cause of the secondary cancers is not known at
this time.