Chemotherapy
Over the last thirty years, the treatment of retinoblastoma has changed
considerably. Previously, when a child was diagnosed with retinoblastoma, few
treatment options were available. In the past, eyes with large-sized
retinoblastoma tumors, or tumors located in a visually threatening place were
treated with external beam radiation or
enucleation (surgical removal of the
eye). There was little opportunity for children to keep their affected eye(s)
or maintain much of their vision. Today, however, the treatments available to
children with retinoblastoma are numerous and continually developing.
Recently
a number of important improvements with chemotherapy have
made it a highly effective treatment for controlling retinoblastoma. It has
become an important component of the retinoblastoma treatment protocol at HSC.
What is Chemotherapy?
Chemotherapy is a combination of anti-cancer drugs that can be an
effective treatment for large retinoblastoma tumors that cannot be controlled by
focal treatments. It is also used for small tumors that are located on or near
the macula. Chemotherapy shrinks tumors without scaring the retina like
laser
and cryotherapy. Chemotherapy is always followed by a plan of laser and cryotherapy. The chemotherapy shrinks the tumors down to a more manageable size
and or away from visually important areas such as the macula, improving the
visual potential of each child.
The size, severity and location of the tumors will largely determine
whether or not your child will require chemotherapy as part of his treatment.
Chemotherapy is given intravenously through a device called a
port-o-cath.
A port-o-cath is a small device that is surgically inserted under the skin in
the childs chest and is attached to large blood vessels. The chemotherapy
drugs are delivered through the skin directly into the port-o-cath and to the
bloodstream. The chemotherapy drugs then travel through the bloodstream and
enter the blood supply of the tumor. The insertion of the port-o-cath is
done in the operating room while your child is asleep under anaesthetic.
How Long is Chemotherapy Treatment?
Generally the number and size of the tumors will determine how much chemotherapy
your child will receive, Chemotherapy treatment is described in terms of
cycles One cycle refers to the delivery of the chemotherapy over 2 full days.
Although treatment is given over 2 days, you and your child can go home at night
between day one and day two of a cycle. Chemotherapy cycles are given at 3-week
intervals. The usual number of cycles of large tumors or tumors with
vitreous seeding and or a
retinal detachment, is 7 cycles of
chemotherapy that are administered over 21 weeks. Medium, or small tumors
usually have about 4 cycles of chemotherapy which is given over a 12 week
period.
While your child is on chemotherapy he will have to have his
blood counts monitored twice a week. Only a small amount of blood is need
and is taken from his finger by a small pin prick. When children are on
chemotherapy they can be at an increased risk for infection. By monitoring
their blood counts, the doctors can keep an eye on the health of the child and
detect problems before they become too serious.
In the couple of days following each chemotherapy cycle, your child
will have an EUA, so that the doctors can monitor the tumor response to the
drugs and to apply an additional laser or cryotherapy to maximize the treatment
effect.
When your child has finished a prescribed number of chemotherapy
cycles, his port-o-cath will be left in place for at least a year after the date
of the last chemotherapy cycle. At some point during the treatment, your
childs tumor(s), may start growing again and may not be controlled by laser
therapy alone. In these cases, it is often suggested that he receive another
1-2 cycles of chemotherapy and then resume the laser therapy when the tumors
have again shrunk. Even if your child does not receive more chemotherapy, his
port will be left in place for some time. He does not feel any discomfort from
it and it requires minimal maintenance (you can speak with the nurses in
Oncology about the long-term care of the port-o-cath).
What Are The Side Effects to Chemotherapy?
The anti-cancer chemotherapy drugs will cause
some other side effects. Your child may develop nausea and vomiting,
constipation or diarrhea, temporary hair loss and low blood counts. Medicines
are available to reduce nausea and vomiting. The drug doses and schedule will
be changed if blood counts are too low. A comprehensive list of all of the
potential side effects caused by the various chemotherapy drugs has been
compiled and is provided at the back of this booklet.
Retinoblastoma Research-The RBS Clinical
Trial
While chemotherapy has been shown to be an effective treatment for
retinoblastoma, the best combination of chemotherapy drugs is not yet known.
Because of this, many university centres such as the Hospital for Sick Children
have formed a group called the Retinoblastoma Study Group (RBS). Over
the next few years we will work together to compare two kinds of treatment. You
may be asked to participate in this International research study. All families
who are eligible will be shown a consent for the study and may or may not choose
to participate. If you consent to be part of the study, each centre will
randomize (similar to tossing a coin) the children requiring chemotherapy into
one of two schedules of treatment. The effectiveness of the treatments will be
compared over several years. In this way, over time we will learn what is the
very best treatment for these children, both to save eyes and to treat tumor
cells that have spread outside of the eye.
