Chemotherapy for Retinoblastoma
Chemotherapy (chemo) is the use of anti-cancer drugs to treat retinoblastoma.
Ways of giving chemotherapy
Chemo can be given in different ways.
Systemic chemotherapy: In most cases, chemo drugs are injected into a vein (IV) or given by mouth. These drugs enter the bloodstream and reach throughout the body. This is known as systemic chemotherapy.
Periocular (subtenon) chemotherapy: For some advanced intraocular cancers, higher doses of chemo are needed inside the eye. Along with systemic chemotherapy, one of the drugs (carboplatin) may be injected in the tissues around the eye, where it slowly diffuses into the eyeball. This is called periocular or subtenon chemotherapy. These injections are done while the child is under anesthesia (asleep). This can cause redness and swelling around the eye.
Intra-arterial chemotherapy: A newer approach sometimes used instead of systemic chemotherapy is to inject chemo directly into the ophthalmic artery, the main artery that supplies blood to the eye. In this technique, a very thin catheter (a long, hollow, flexible tube) is inserted into a large artery on the inner thigh and slowly threaded through the blood vessels all the way up into the ophthalmic artery. (This is done with the child asleep under general anesthesia.) The chemo is then infused into the artery. The drug used most often is melphalan, but other drugs such as carboplatin and topotecan can also be used. This process may then be repeated every few weeks, depending on how much the tumor shrinks.
Because the chemo is put directly into the artery feeding the eye, doctors can use much smaller doses of chemo drugs (less than 10% of the doses used for systemic chemo). Therefore, there are fewer side effects from the chemo.
Early results with this technique in eyes with advanced tumors have been promising, generally with good tumor control and few side effects. In most cases it has allowed doctors to save an eye that otherwise would have needed to be removed.
Intravitreal chemotherapy: In this newer approach, chemotherapy is given directly into the vitreous humor, the jelly-like substance inside the eye. This approach is discussed in the section “ What’s new in retinoblastoma research and treatment?”
Uses of chemotherapy
Chemotherapy may be used in different situations:
- Chemo can be used as the first treatment to shrink some tumors that have not spread outside the eye. This is called chemoreduction. These tumors can then be treated more effectively with focal therapies such as laser therapy, cryotherapy, thermotherapy, or brachytherapy.
- Systemic (IV) chemo may be given to children whose tumors don’t seem to have spread beyond the eye, but might be likely to spread because of the tumor’s size and/or location.
- Chemo is sometimes used when the eye has already been removed, but the tumor was found to extend into some areas in the eye that make it more likely to have spread. This type of treatment is called adjuvant chemotherapy.
- Systemic chemo is also used to treat children whose retinoblastoma has spread beyond the eye, a much more critical situation. If the cancer has spread to the brain, chemo may also be given directly into the cerebrospinal fluid that surrounds it (known as intrathecal chemotherapy). Tumors outside the eye may shrink for a time with standard doses of chemo, but they will usually start growing again. For this reason, doctors often prefer to give more intense chemo, usually along with a stem cell transplant. (See the section “ High-dose chemotherapy and stem cell transplant.”)
Doctors give systemic chemo in cycles, with each period of treatment followed by a rest period to give the body time to recover. Each chemo cycle typically lasts for a few weeks, and the total length of treatment is often several months.
Some of the drugs used to treat children with retinoblastoma include:
Most often, 2 or 3 drugs are given at the same time. A standard combination used to shrink intraocular retinoblastomas is carboplatin, vincristine, and etoposide, although for very small tumors, only carboplatin and vincristine may be enough. Other drugs might be used if these are not effective.
Possible side effects
Chemo drugs attack cells that are dividing quickly, which is why they work against cancer cells. But other cells in the body, such as those in the bone marrow (where new blood cells are made), the lining of the mouth and intestines, and the hair follicles, also divide quickly. These cells are also likely to be affected by chemo, which can lead to side effects.
Children tend to have less severe side effects from chemo and to recover from side effects more quickly than adults do. One benefit of this is that doctors can give them the high doses of chemo needed to kill the tumor.
The side effects of chemo depend on the type of drugs, the doses used, and how long they are given. Possible short-term side effects include:
- Hair loss
- Mouth sores
- Loss of appetite
- Nausea and vomiting
- Diarrhea or constipation
- Increased chance of infections (from having too few white blood cells)
- Easy bruising or bleeding (from having too few blood platelets)
- Fatigue (from having too few red blood cells)
Most of these side effects go away after treatment is finished. There are often ways to lessen these side effects. For example, drugs can be given to help prevent or reduce nausea and vomiting. Be sure to discuss any questions about side effects with your child’s cancer care team, and let them know if your child has side effects so they can be managed.
Along with those listed above, certain chemo drugs can cause specific side effects. For example:
- Cisplatin and carboplatin can affect the kidneys. Giving the child plenty of fluids during treatment can help reduce this risk. These drugs can also cause hearing loss in young children, especially in babies younger than 6 months. Your child’s doctor may check your child’s hearing with tests during or after treatment. When carboplatin is injected directly into the tissues near the eye (periocular chemotherapy), it can cause redness and swelling in the area.
- Vincristine can damage nerves. Some children may feel tingling and numbness, particularly in their hands and feet.
- Some drugs, such as etoposide, doxorubicin, and cyclophosphamide, can increase the risk of developing a cancer of white blood cells known as acute myeloid leukemia (AML) later in life. Fortunately, this is not common.
- Doxorubicin can damage the heart. The risk of this happening goes up with the total amount of the drug given. Doctors try to limit this risk as much as possible by not giving more than the recommended doses and by checking the heart with an echocardiogram (an ultrasound of the heart) during treatment.
- Cyclophosphamide can damage the bladder, which can cause blood in the urine. This risk can be lowered by giving this drug along with plenty of fluids and with a drug called mesna, which helps protect the bladder.
For more information about chemotherapy, see A Guide to Chemotherapy.
Last Medical Review: March 12, 2015 Last Revised: March 12, 2015
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