Research on retinoblastoma is being done at many medical centers, university hospitals, and other institutions across the world.

Genetics, genetic counseling, and gene therapy

The defective gene responsible for retinoblastoma (the Rb gene) was identified in 1986. This discovery, together with technical advances in analyzing DNA changes, has made genetic testing a possibility.

A great deal of research has gone into figuring out how certain DNA changes in retinal cells cause them to become cancerous. Scientists understand these changes better for retinoblastoma than for most other cancer types. Although probably still years away, researchers hope that this understanding will one day lead to gene therapies, very specific treatments that can repair or counteract these DNA changes.

Treatment

Research is continuing the progress made in treating retinoblastoma over the past few decades.

Radiation therapy

External radiation therapy can effectively treat retinoblastoma, but it can cause side effects because the radiation often reaches nearby tissues as well. Newer forms of radiation therapy are better able to target the tumor yet spare nearby tissues.

For example, intensity modulated radiation therapy allows doctors to better control the shape and intensity of the radiation beams to minimize nearby effects.

Another technique now being studied is proton beam therapy. Protons are positive parts of atoms. Unlike the x-rays used in standard radiation, which release energy both before and after they hit their target, protons cause little damage to tissues they pass through and then release their energy after traveling a certain distance. This means that proton beam radiation may be able to deliver more radiation to the tumor and cause less damage to nearby normal tissues. Early results with proton beam therapy are promising, but there is very little long-term data on its use for retinoblastoma. The machines needed to make protons are expensive, and there are only a handful of them in use in the United States at this time.

Other local treatments

Doctors are continually improving the instruments used for cryotherapy, laser therapy, and other local treatments. The goal is to more precisely kill tumor cells while sparing other parts of the eye.

Chemotherapy

Chemotherapy has played a more prominent role in treating many retinoblastomas in recent years.

Systemic chemotherapy: Chemotherapy is now commonly used to shrink tumors before local treatments such as cryotherapy or laser therapy. Doctors are now studying whether giving chemotherapy after local treatments (known as adjuvant chemotherapy) might help prevent the recurrence of retinoblastoma, especially outside the eye. Doctors are also studying the use of different chemotherapy drugs such as topotecan, as well as new ways of combining current drugs, to try to improve the effectiveness of chemotherapy.

Localized chemotherapy: Chemotherapy can help shrink most retinoblastomas, but because it is given into the bloodstream it can cause side effects in different parts of the body. This limits the doses that can be given.

Doctors are studying injecting the chemotherapy around the diseased eye (known as subconjunctival, subtenon, or periocular chemotherapy). This might allow higher doses of chemotherapy to reach the tumor while limiting side effects elsewhere. Although there has been some success, many doctors still consider this to be an experimental approach. New methods for periocular delivery are being studied, including placing small reservoirs loaded with chemotherapy outside the eye, which would release the drug into the eye for prolonged periods. If it proves to be useful, it will most likely be combined with other treatments.

Another new approach is to inject chemotherapy directly into the ophthalmic artery, the main artery feeding 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 all the way up into the ophthalmic artery. (This is done with the child under general anesthesia.) The chemotherapy is then infused into the artery. Early results with this technique have also been promising, although further study is needed.

High-dose chemotherapy and stem cell transplant: Retinoblastomas that have spread widely are much harder to treat than those still confined to the eye. The doses of chemotherapy that can be given are limited by the side effects they cause, especially in the bone marrow (where new blood cells are made). Researchers are now testing the value of giving very high-dose chemotherapy, followed by a stem cell transplant to replace the body's bone marrow cells, which were killed by the chemotherapy. Several clinical trials are studying this approach.

Last Medical Review: 10/26/2009
Last Revised: 10/26/2009