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Retinoblastoma is a rare type of ocular cancer that develops in the retina of the eye. It is a type of blastoma, which are cancers that develop in precursor cells, most often in children. It can occur in one eye (unilateral retinoblastoma, usually non-hereditary), or in both eyes (bilateral retinoblastoma, often hereditary).
The eye is a sensory organ that allows us to see by reacting to light. Light passes through the cornea (the clear, front layer of the eye) and enters the eye through an opening called the pupil (the black centre of the eye). The amount of light received by the pupil is controlled by the iris (the coloured portion of the eye). This light is then passed through the lens (the clear, inner portion of the eye) and works together with the cornea to focus light onto the retina (a layer of tissue at the back of the eye that is sensitive to light). The retina then activates photoreceptors (image forming cells) to convert the light to electrical impulses that travel to the brain via the optic nerve, which is then converted into an image.
Retinoblastomas are generally found equally between the genders, and is usually diagnosed before the age of five. However, anyone can develop this disease.
Retinoblastomas can be classified in a few different ways.
Hereditary retinoblastomas are tumours that have developed in patients with a family history of the disease. In most cases, this is due to a genetic mutation in the retinoblastoma tumour suppressor gene (RB1). Hereditary retinoblastomas are generally bilateral (affect both eyes).
Non-hereditary retinoblastomas are the most common subtype of this disease. They are non-hereditary, and may be the result of a random genetic mutation. In most cases, non-hereditary retinoblastomas are unilateral (only affect one eye), and are diagnosed at a later stage than hereditary retinoblastomas.
Intraocular retinoblastomas are cancers that are solely located in one or both of the eyes, and have not metastasized (spread).
Extraocular retinoblastomas are cancers that have spread beyond the eye into nearby tissues and organs.
If a retinoblastoma is detected, it will be staged and graded based on size, metastasis (whether the cancer has spread to other parts of the body) and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you.
There are two primary staging and grading systems used in the classification of retinoblastomas – The International retinoblastoma staging system and the TMN system.
The international classification for intraocular retinoblastoma (ICIR) divides intraocular cancer into five groups based on the characteristics of the tumour. These groups include:
The TNM system can also be used to classify a retinoblastoma. This system is beneficial for all types of retinoblastomas, including extraocular tumours. The TNM system is comprised of:
This system can also be used in combination with a numerical value, from stage 0-IV:
Cancers can also be graded based on the rate of growth and how likely they are to spread:
Once your tumour has been staged and graded, your doctor may recommend genetic testing, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, stage of disease and overall health.
Treatment options for retinoblastomas may include:
For more information on the treatment options, please refer to the Rare Cancers Australia Treatment Options page.
Because of how rare retinoblastomas are, there has been limited research into the risk factors of this disease. However, few potential factors have been identified:
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
The symptoms of retinoblastoma may include:
Not everyone with the symptoms above will have cancer but see your general practitioner (GP) if you are concerned.
If your doctor suspects you have an ocular melanoma, they will order a range of diagnostic tests to confirm the diagnosis, and refer you to a specialist for treatment.
The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), and/or ultrasound, depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.
Your doctor may request a variety of eye tests to check for abnormalities in your eye. One of these tests is called an ophthalmoscopy (fundoscopy), which involves using eye drops to widen your pupil and then looking into a large microscope. This option is beneficial as you may not require a biopsy after this test.
Another test, called a fluorescein angiography, examines the blood vessels and blood flow in the eye. This procedure is done by injecting a fluorescent dye into the bloodstream, which travels to the eye. A special camera is used to determine if there are any blocked or leaking vessels in the eye.
The doctor may also request an electroretinography, which measures small electrical signals given off by the eye when exposed to different types of light. This test can be used to measure the effectiveness of the retina during and/or after treatment.
In few instances, a biopsy may be required if the previous measures have come back inconclusive. In a biopsy, a tissue sample will be removed using a needle, and is then sent to a lab for analysis.
While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, early-stage retinoblastomas have a better prognosis and survival rates. However, if the cancer is advanced and has spread, the prognosis may not be as good and there may be a higher risk of cancer recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis.
Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.
Page last updated: 02/05/2022