What is retinoblastoma?

Retinoblastoma is a rare type of cancer in the eye that initially starts in the retina.

Considered the most common type of eye cancer in children, retinoblastoma forms when retinoblasts — immature cells in the eye — continue to divide and grow out of control.

Normally, the retinoblastoma (RB1) gene found in retinoblasts prevents this uncontrolled growth. However, a mutation in the RB1 gene causes a malfunction, leading to one of two different types of retinoblastoma.

Types/subtypes

Retinoblastoma is broken down into hereditary or non-hereditary disease.

The hereditary form — which occurs in nearly one out of three children with retinoblastoma — is known as congenital retinoblastoma. In those cases, a mutation in the RB1 gene is present at birth. A germline mutation is found in both retinas, as well as in all cells of the child’s body.

Retinoblastoma that develops in both eyes is known as bilateral retinoblastoma, and children often have several tumors within the eye (multifocal retinoblastoma).

Children with congenital retinoblastoma are at increased risk for other cancers that develop in different areas of the body. In some cases, another tumor will develop in the brain — most often in the pineal gland at the base of the brain — and is known as a pineoblastoma or trilateral retinoblastoma.

When the mutation in the RB1 gene develops on its own in only one cell in one eye, the child has what is known as sporadic or non-hereditary retinoblastoma. This occurs in nearly two out of three children with retinoblastoma. Experts are unaware of what causes this mutation to occur.

Sporadic or non-hereditary retinoblastoma often is discovered in older children. The elevated risk for other types of cancers is not as high among children with sporadic or non-hereditary retinoblastoma as it is for children with congenital retinoblastoma.

Risk factors and symptoms

There are few known risk factors for retinoblastoma.

For most cases, there is no family history of the disease. The mutation is inherited by a parent in only 25% of cases. In nearly 75% of cases, a mutation in the RB1 gene first occurs during the developmental stages in the mother’s womb.

Retinoblastoma is uncommon among older children and adults. The majority of cases are diagnosed in children aged younger than 3 years. Congenital retinoblastoma is most often diagnosed within the first year of a child’s life, whereas sporadic retinoblastoma is more often detected at age 1 or 2 years.

White pupillary reflex, the most common early symptom of retinoblastoma, is detected when a pupil appears white or pinkish instead of red when a light is projected in the eye. Parents may notice this when their child’s pupils are different colors when flash photography is taken, or a physician may notice this during a routine eye exam, according to the American Cancer Society.

Lazy eye is another common symptom of retinoblastoma; however, this condition also can be caused by a slight weakness in the eye muscles.

Other uncommon symptoms include eye pain, vision problems, bleeding in the front part of the eye, redness in the white part of the eye, eye bulge, different color in each iris or pupils that do not decrease in size when exposed to bright light.

Treatment

If retinoblastoma tumors are left untreated, they may multiply in the eye and tumors may eventually block the channels that allow fluid to flow within the eye, causing a rise in pressure inside the eye. This may lead to glaucoma, pain and/or loss of vision.

However, the majority of cases are identified and treated early, and more than 90% of cases are cured.

The American Cancer Society recommends children with retinoblastoma receive treatment at a specialty eye hospital or a major children’s cancer center. These centers have specialists — such as pediatric ophthalmologists, ocular oncologists, pediatric oncologists and radiation oncologists — who are experienced in the treatment of retinoblastoma.

Treatment may consist of one or more of the following: chemotherapy, cryotherapy, high-dose chemotherapy and stem cell transplant, photocoagulation, radiation therapy, surgery and thermotherapy.

Looking ahead

Although significant advances in research for retinoblastoma have led to higher cure rates during the past few decades, not all cases are cured and some children who are cured experience long-term side effects from treatment.

For this reason, research on retinoblastoma is ongoing. For example, studies are underway to assess how certain mutations in DNA in retinoblasts lead to cancer, and researchers hope this understanding will lead to the development of gene therapies.

Other major goals include the improvement of tools used for cryotherapy, laser therapy and thermotherapy to specifically target tumor cells and save other areas of patients’ eyes.

More information is available at these websites:

www.cancer.org/cancer/retinoblastoma/detailedguide/retinoblastoma-what-is-retinoblastoma