Retinoblastoma is the most frequently occurring neoplasm of the eye in childhood. Retinoblastoma is a type of cancer that starts in the retinoblasts of the eye. Simply put, the term retino refers to retina (part of the eye), whilst blastoma means a cancer that involves immature or developing cells. It is basically a childhood tumour occurring in the very young age group, that is mostly 2 to 5 years of age and less. They account for 3% of childhood cancers.
What do we know about the eye ?
The major part of the eye consists of the eyeball (otherwise called the globe), which is packed with a jelly-like substance, the vitreous humour. The front part of the eyeball has a lucid clear lens with an iris (the iris is the coloured part of the eye, that acts as a camera shutter), allowing light to enter eye and focusing it on retina. The retina is the inside layer of cells located in the back of the eye. It is made up of unique nerve cells (rods & cones) that are perceptive to light. These rods and cones are in turn linked to the brain by a special nerve, called the optic nerve. The image that is received by the retina is transmitted through the optic nerve to the brain, allowing us to see.
What are the causes of retinoblastoma ?
Most retinoblastomas are sporadic (non-hereditary) cancers but there are familial retinoblastomas (hereditary) cancers as well. Researchers have found changes (mutations) in a gene called the retinoblastoma (RB1) gene. The normal RB1 gene keeps cells from dividing out of control, but the mutated gene is unable to control cell division. Depending on the mutation or change in the RB1 gene, 2 different types of retinoblastoma can result.
What are the types of retinoblastoma ?
- Congenital or hereditary retinoblastoma: Congenital means present at birth. In congenital retinoblastoma, the abnormality in the RB1 gene is present at birth and is seen in all of the body’s cells, including both the retinas. This is otherwise known as germline mutation. In most of the congenital retinoblastomas, there is no family history of this cancer. Only a quarter of the children with this mutated gene inherit it from parents. In most children the genetic change initially occurs during early womb development. Children born with a mutated RB1 gene typically get retinoblastoma in both the eyes (called bilateral retinoblastoma), and sometimes there are several tumours within the eye (known as multifocal retinoblastoma).
- Sporadic (non-hereditary) retinoblastoma: In most retinoblastomas, the mutation in the RB1 gene develops by itself in only one cell in a single eye. It is not really known what causes this. A child with sporadic or non-hereditary retinoblastoma gets the tumour in only one eye. This type of retinoblastoma occurs at a later age than the hereditary form.
What are the clinical features of retinoblastoma ?
Retinoblastomas are almost always found in young children. Most are often noticed when the parent or the doctor notices that a child’s eye looks abnormal.
- White Pupillary Reflex: This is the commonest indicator of retinoblastoma. In general, when you reflect a light in the eye, the center dark pupil appears to be red because of the presence of blood vessels at the back of eye. An eye affected with retinoblastoma will show white or pink pupils instead, otherwise known as the white pupillary reflex.
- Lazy Eye: If the eyes don’t seem to be looking in one direction, it is called lazy eye or strabismus. It could be because of harmless causes or it could be because of retinoblastoma.
Less common symptoms of retinoblastoma are problems in vision, pain in the eyes, redness of eyes and bleeding in the eyes.
How is retinoblastoma diagnosed ?
- A complete physical examination of the body is mandatory.
- Imaging Tests: Important diagnostic tests include the following such as Ultrasound, CT Scan or MRI Scan. Ultrasound is one of the imaging tests used most often for diagnosis of retinoblastoma. Magnetic Resonance Imaging (MRI) & Computed Tomography (CT) Scans are the imaging tests that can be used as well for diagnosis of eye tumours.
- Lumbar Puncture (spinal tap): This test looks for cancer cells in the cerebrospinal fluid (CSF), the fluid that surrounds the brain and spinal cord.
- Biopsy: For most cancers, removed tissue examined under a microscope by a pathologist is the only sure-shot way to make a definitive cancer diagnosis. However, taking a biopsy of a tumour at the interior part of the eye can often cause eye damage as well as seed tumour cells, so this is rarely done to diagnose retinoblastoma. Doctors arrive at the diagnosis based on eye exams and on imaging tests.
How are retinoblastomas staged ?
Firstly, the tumours are staged locally and systemically. There are different treatments required at different stages of disease. Moreover prognostic factors influence treatment strategies.
The stages of Retinoblastoma are as under.
- Intraocular Retinoblastoma: The cancer is located in the eye.
- Extraocular Retinoblastoma: The cancer has gone beyond the extent of the eye.
These are again divided into either orbital retinoblastomas, which extend within the eye socket, or metastatic retinoblastomas, which have extended to distant body parts like the brain or bone marrow.
How are retinoblastomas treated ?
Retinoblastomas are rare. An ocular oncologist, pediatric oncologist, radiation oncologist and a neurosurgeon will have to be consulted, and either a single therapy or a combination of treatments will be decided for your child. The treatments for Retinoblastoma include ;
- Surgery : If vision is already affected or lost, the treatment is enucleation, a surgery done under general anaesthesia to remove the whole eye, plus the optic nerve extending from it.
- Radiation Therapy : a cancer treatment that utilizes high-energy x-rays or basically radiation to eradicate cancer cells. Radiation can be used on select patients if surgery is not a good option. Radiation therapy can also be used post surgery to kill any remaining cancer cells.
- Photocoagulation : This uses lasers to eliminate small tumours or even the blood vessels that supply them.
- Cryotherapy : This uses cold temperatures to freeze and eliminate small tumours.
- Thermotherapy : This uses laser therapy to apply heat to remove small tumours.
- Chemotherapy : another kind of cancer treatment that uses either drugs or chemical substances (hence the name chemotherapy) to kill cancer cells and prevent them from dividing.
What is the care to be taken after the removal of a retinoblastoma ?
Once treatment is over, your child will be put on a follow-up schedule. It is crucial to attend all follow-up appointments. Metastatic diagnostic workup and monitoring post-treatment for aggressive or disseminated retinoblastomas includes imaging and scanning of the body with MRI or CT scans.
How can retinoblastomas be prevented ?
If there is a family history of retinoblastoma, consult a genetic counsellor about the children’s risks of having the disease.
How to find and reach cancer specialists for retinoblastoma treatment ?
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Disclaimer: The content provided here is meant for general informational purposes only and hence SHOULD NOT be relied upon as a substitute for sound professional medical advice, care or evaluation by a qualified doctor/physician or other relevantly qualified healthcare provider.
