What’s new in retinoblastoma research and treatment?
Over the past few decades, research into retinoblastoma has led to great advances and much higher cure rates for this type of cancer. Still, not all children are cured, and even those who are cured might still have long-term side effects from treatment, so more research is needed.
Research on retinoblastoma is being done at many medical centers, university hospitals, and other institutions around the world.
Genetics, genetic counseling, and gene therapy
The defective gene responsible for nearly all retinoblastomas (the RB1 gene) was identified in 1986. This discovery, along with technical advances in finding DNA changes, has made genetic testing possible.
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.
For example, researchers have recently found that an oncogene known as SYK is overactive in retinoblastoma cells. Drugs that target the protein this gene makes are now being developed. Another gene called MDM4 also seems to be involved in the development of retinoblastoma, and drugs aimed at blocking its effects are being studied.
Recently, researchers have found that a very small portion of retinoblastomas do not seem to have changes in the RB1 gene, but instead have too many copies of another gene called MYCN. It is not yet clear if these cancers are different in any important ways from those with RB1 gene changes.
Research is building on the progress made in treating retinoblastoma over the past few decades.
External radiation therapy can be used to treat retinoblastoma, but it can cause side effects because the radiation often reaches nearby tissues as well. This limits its usefulness. Newer forms of radiation therapy such as intensity modulated radiation therapy (IMRT) and proton beam therapy are better able to target the tumor yet spare nearby tissues. These techniques, which are described in the section “Radiation therapy for retinoblastoma,” may help doctors limit the side effects from radiation therapy.
Other local treatments
Doctors continue to improve the instruments used for cryotherapy, laser therapy, thermotherapy, and other local treatments. The goal is to kill tumor cells more precisely while sparing other parts of the eye.
Chemotherapy (chemo) has played a larger role in treating many retinoblastomas in recent years.
Chemo given into a vein (IV) is now commonly used to shrink tumors before local treatments such as cryotherapy or laser therapy. Doctors are now studying whether giving chemo 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 chemo drugs such as topotecan, as well as new ways of combining current drugs, to try to improve how well chemo works.
Chemo can help shrink most retinoblastomas, but when 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. Newer techniques help keep the chemo concentrated in the areas around the tumors. This might help doctors get higher doses of chemo to the tumors while reducing some of these side effects. Some of these were described in the section “Chemotherapy for retinoblastoma”.
Subtenon (subconjunctival or periocular) chemotherapy: Doctors are studying injecting the chemo into the area around the eye. This might allow higher doses of chemo to reach the tumor while limiting side effects elsewhere. There has been some success, but 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 useful, it will most likely be combined with other treatments (including systemic chemotherapy).
Intra-arterial chemotherapy: In this approach, chemo is injected directly into the ophthalmic artery, the main artery feeding the eye, using a long, thin catheter. When intra-arterial chemotherapy is used, the dose of the chemo drug is much lower than when is given by vein, and the side effects related to the chemo are minimal.
Early results with this technique in eyes with advanced tumors have been promising, with good tumor control and few side effects in most cases. In most cases it has allowed doctors to save an eye that otherwise would have needed to be removed. Some doctors are already using this approach, although further study is needed to be sure it is safe and effective.
Intravitreal chemotherapy: Some doctors are studying injecting chemotherapy directly into fluid inside the eyeball (the vitreous) to treat tumors that are widespread within the eye and not helped by other treatments. The main concern with this technique is that placing the needle into the eye to give the chemo might open a small hole that could allow tumor cells to spread outside of the eye, so doctors are being very cautious with this approach. It is still in very early stages of testing and is not commonly used.
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 chemo 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: 12/05/2013
Last Revised: 12/05/2013