Diagnosis and Staging
Correctly staging retinoblastoma is vital to define most appropriate medical care for the child.
Various tests are used to diagnose retinoblastoma and find out more about the cancer, such as number, size and position of tumours, and whether cancer has spread outside the eye. This process is called staging, and helps doctors decide which treatments are most appropriate.
There is no blood test to diagnose retinoblastoma, only genetic testing to predict risk when a relative has retinoblastoma. Blood tests will be done to check your child’s general health and their body’s ability to tolerate proposed treatments.
The ophthalmologist uses dilating drops to make the pupil bigger so they can clearly see the back of each eye. A vision test, ultrasound and eye pressure test may also be done for both eyes.
An examination under anaesthetic (EUA) will be done to carefully check both eyes while your child is asleep. EUA is usually done on a day surgical unit, but your child may be admitted overnight if she is an infant or has other medical conditions.
Retinoblastoma is rare among cancers because it can be diagnosed based on what the doctor observes on clinical exam and imaging tests. A biopsy (tissue sample) is not needed, and may actually allow tumour cells to spread outside the eye. The tumor is only safely studied after the eye has been removed.
A blood sample may be taken for genetic analysis of the RB1 gene. Results can take several months, but they help to establish if both eyes, and other blood relatives are at risk. This specialist genetic test is available at a small number of expert centres around the world, and the ability of each lab to find the RB1 mutations is an important quality control. Samples may be sent internationally for testing.
MRI and CT scans take a series of pictures that show the structures of the eye and brain. They check for spread of cancer outside the eye, and for rare trilateral retinoblastoma. Babies and young children usually receive a short acting general anaesthetic as they must lay very still, and the scan can take up-to 90 minutes.
While in some places CT must be done because MRI is not available, CT is generally no longer recommended for children with retinoblastoma because it uses radiation to collect the image.
A lumbar puncture removes a small sample of cerebrospinal fluid, (fluid bathing the brain and spinal cord). This fluid is examined under a microscope to see if any cancerous cells have spread from the eye to the brain.
A bone marrow aspiration or biopsy removes a small sample of marrow, usually from the hip bone. Marrow is the spongy material inside our bones, that makes blood cells. The sample is examined under a microscope to find out if cancerous cells have spread to the bone marrow.
Staging cancer summarizes the information doctors gain from various tests and examinations. This process helps the medical team and patient families define potential for cure and eye salvage before treatment begins, and identify the best treatment options.
Retinoblastoma is staged to predict how effective different treatments are to save the child’s life. Each eye is staged to indicate likelihood that different treatments can safely save the eye, and achieve best vision. Cancer stage for a bilaterally affected child is based on the worst affected eye, as an indicator of risk to the child’s life.
Several different systems are used to stage retinoblastoma. Learn about them here.
Tests usually take place over several days. They are more effective and less traumatic when the child has good child life support.
All tests and investigations should be clearly explained to you before they are done. Do not be afraid to ask questions – it is important that you understand what will happen so you can be prepared and support your child. Click on the links to find out more about individual procedures.
What and who you take to the first hospital visits can have a huge impact on your child’s comfort, and your own. These hospital packing tips from parents will help you and your child feel calmer and more comfortable at this very difficult time.