Chemotherapy for Retinoblastoma
Chemotherapy for retinoblastoma is given in several ways.
Intravenous (IV): also called “systemeic chemotherapy“, cancer-fighting medications are delivered into the bloodstream via an IV cannula in the arm or hand, or through a central venous catheter. This is the most common form of chemotherapy for retinoblastoma, and the focus of this section.
Intra-Artertial (IAC): infused directly into the eye via the ophthalmic artery, reached by a catheter inserted into the femoral artery. Used to treat medium to large sized intra-ocular retinoblastoma when there is no risk that tumour can spread outside the eye.
Intravitreal (IViC): injected directly into the fluid middle of the eye to treat vitreous seeds (fragments of cancerous cells that break off the main tumour and float into the fluid). Used in combination with other treatments, injections begin only after the main tumour producing the seeds is controlled.
Periocular: delivered directly to the tissues or space surrounding the eye, used in combination with other therapies to treat medium and large tumours that are not at risk to escape the eye.
Intrathecal (IT): injected into the cerebrospinal fluid (fluid bathing the brain and spine), circumventing the blood-brain barrier. Used to treat trilateral retinoblastoma and when cancer has spread from the eye to the brain.
Oral (PO): taken by mouth in liquid, capsule or tablet form, and absorbed into the blood through the lining of the stomach and intestines. This form of chemotherapy is sometimes used in palliative care for retinoblastoma.
This section focuses on intravenous chemotherapy. To learn more about the other forms of chemotherapy, click the links above.
When Intravenous Chemotherapy Is Used
Chemotherapy is usually prescribed:
- for eye-salvage when both eyes are affected, there is no risk of cancer escaping the eye and some vision may be saved.
- after enucleation when pathology finds clear evidence that cancer has escaped the eye
- before or after enucleation when tests (MRI, CT, lumbar puncture or bone marrow aspirate) show cancer has spread beyond the eye
- before or after enucleation when the eyeball is bulging or ruptured
- when the child has trilateral retinoblastoma
- to manage pain and minimize symptoms when the child is dying
In eye salvage treatment, chemotherapy shrinks tumours so they can be eradicated with focal therapies. Chemotherapy is sometimes used for unilateral retinoblastoma when tumours are small with a good chance of preserving useful vision in the eye.
Length of Treatment
A course of intravenous chemotherapy involves a number of cycles. For retinoblastoma, a cycle is usually 2 – 3 days of treatment and a ‘rest’ period of 3 – 4 weeks that allows the body to recover from the effects of the drugs.
The number of cycles will depend on your child’s protocol, the reasons for treatment, how well your child is, and how the tumour(s) respond. Doctors will constantly check tumour response and your child’s health with EUAs, MRI scans, blood tests and other investigations.
Most children receive 4-6 cycles of intravenous chemotherapy. Children with trilateral retinoblastoma or retinoblastoma that has spread to other parts of the body may receive more than a year of chemotherapy.
Chemotherapy damages a cells’ ability to grow or reproduce. As cancer cells multiply rapidly, they are more susceptible than healthy cells. However, rapidly dividing healthy cells can also be damaged, causing side effects.
Vulnerable healthy cells include those found in the bone marrow, hair follicles, mouth, stomach, intestines and skin. Fortunately, they recover quickly so side effects are usually temporary.
The most serious side effect is suppression of the bone marrow, which ms blood cells. Decreased production of red and white blood cells and platelets can cause serious complications such as infection and bleeding. Blood tests will be done regularly during treatment to monitor the health of your child’s bone marrow, and provide early treatment if needed.