Stages of Retinoblastoma

If a child is diagnosed with retinoblastoma, doctors will do tests to figure out if it has spread, and if so, how far. This process is called staging. The stage of the retinoblastoma describes how big a tumor is and where the cancer is in the body.

Retinoblastoma is staged based on the results of eye exams, imaging tests, and any other tests that were done, which are described in Tests for Retinoblastoma.

Retinoblastoma staging

Knowing the stage can help the cancer care team predict if the tumor can be treated in a way that saves the affected eye or the vision in the eye.

When determining the stage, doctors often divide retinoblastomas into 2 main groups:

• Intraocular retinoblastoma: Cancer is only present in the eye.
• Extraocular retinoblastoma: Cancer has spread outside the eye. Extraocular cancers can be divided further into orbital retinoblastomas, which have spread only to the eye socket, and metastatic retinoblastomas, which have spread to distant parts of the body, such as the brain or bone marrow.

In the United States, most retinoblastomas are diagnosed before they have spread outside the eye, so the most common staging system used applies only to intraocular retinoblastoma.

With the right treatment, most children with intraocular retinoblastoma can be cured.

Intraocular retinoblastoma staging

The International Classification for Retinoblastoma is the staging system that most doctors now use. It divides intraocular retinoblastomas into 5 groups, labeled A through E, based on the extent of the cancer and the chances that the eye can be saved using current treatment options.

Group A: Small tumors (no more than 3 millimeters [mm] across) that are only in the retina and are not near important structures, such as the optic disc (where the optic nerve enters the retina) or the foveola (the center of vision).

Group B: All other tumors (either larger than 3 mm or close to the optic disc or foveola) that are still only in the retina.

Group C: Well-defined tumors with small amounts of spread under the retina (subretinal seeding) or into the jelly-like material that fills the eye (vitreous seeding) near the tumor (less than 3 mm from the tumor).

Group D: Large or poorly defined tumors with widespread (more than 3 mm from the tumor) vitreous or subretinal seeding. The retina may have become detached from the back of the eye.

Group E: The tumor is very large, extends near the front of the eye, is bleeding or causing glaucoma (high pressure inside the eye), invades the optic nerve or orbit, or has other features that mean there is almost no chance the eye can be saved.

While group A eyes can be saved with current treatments, with each progressive letter, the chance of saving the eye is reduced. In the past, group E eyes were almost always removed as part of initial treatment. Now, with newer ways to treat retinoblastoma, these eyes might have a chance of being saved as well. For more information, visit Treating Retinoblastoma.

Other staging systems that can be used for tumors that have spread outside the eye

Other staging systems that include both intraocular and extraocular retinoblastomas may be used. These can be especially useful in countries where these cancers are more likely to have spread by the time they are found.

American Joint Commission on Cancer (AJCC) staging system

This system includes 4 key pieces of information:

• T: The size of the main (primary) tumor and how far it has grown within and outside of the eye by clinical exam or pathology (if the eye has been removed).
• N: Whether the cancer has reached nearby lymph nodes (small, bean-shaped collections of immune cells to which cancers sometimes spread) in the head or neck.
• M: Whether the cancer has spread (metastasized) to distant parts of the body, such as the bone marrow, brain, skull, or long bones.
• H: Whether the child has heritable retinoblastoma.

These 4 pieces of information are combined to group retinoblastomas into stages I –IV. This information is used to determine treatment options and predict the ability to save the eye and cure the child of retinoblastoma.

International Retinoblastoma Staging System (IRSS)

This staging system can also be used to describe retinoblastoma that has spread outside the eye and predict survival.

• Stage 0: Eye has not been removed; the cancer has not spread.
• Stage I: Eye removed (enucleation); no cancer cells seen at the edges of the removed eye.
• Stage II: Eye removed (enucleation); cancer cells can be seen with a microscope at the edges of the removed eye but spread cannot be seen with the naked eye.
• Stage III: Cancer is in the orbit surrounding the eye or has spread to the local lymph nodes near the ear or in the neck.
• Stage IV: Cancer is present in the body far from the eye or has spread to the brain or cerebrospinal fluid (CSF).

Understanding your child’s stage is important for choosing a treatment plan and getting a sense of your child’s outlook, both for cure and for saving the affected eye and its vision. The different staging systems used for retinoblastoma are complex and can be confusing. If you are unsure about your child’s stage and what it means, ask your child’s doctor to explain it to you in a way you can understand.