Retinoblastoma is a rare type of eye cancer that start when cells in the retina of the eye start to grow out of control. This is a rare type of eye cancer that affects children. Statistics shows that, these cancers normally affects those under five.
An eye is a sensory organ responsible for collecting light and sending it to the brain to form images. The eye has three main parts which are as follows;
1. Eye ball: sometimes this is called the globe. Eye ball is formed by major three parts also called layers.
2. Sclera: This is the outer most layer of the eye ball. It is whitish with continuation of cornea at the front side of the eye ball.
3. Uvea: This is the middle part(layer) of the eye ball which consist of the following,
4. Iris: This is the colored part of the eye which surrounds the pupil. Like diaphragm of the camera iris controls amount of light reaching the back side of the eye by adjusting the size of pupil (small opening through which light enters the eye)
5. Ciliary body: This part of uvea is formed by muscles that are responsible for adjusting lens of the eye so as to focus on near and distant object.
6. Choroid: Choroid is the part of the eye ball containing cells called melanocytes from which melanoma of the eye originate.
7. Retina: This is the part of the eye where light rays collect to form image. This part contains light sensitive cells that that form nerves called optic nerves which carry image formed in retina to the brain for interpretation.
Cancers that start in the eye ball are also called intraocular cancers which means they originate within the eye.
1. Orbit (eye socket): Orbit can simply be defined as cavity in the skull that encloses eyeball with its surrounding muscles. Cancers that start from this part of the eye are called orbital cancers.
2. Adnexal structures: These are also called accessory structures of the eye. These include structures like tear glands and eyelids. Also cancers affecting these parts are called adnexal cancers.
In this document, we will focus on discussing cancer which start from retina which is one among three layers of the eye ball.
During development of the eye, cells known as retinoblasts divide and develop to maturity to form retinal cells (special cells that detect light). These cells form a layer called retina. But in some rare cases, these cells fail to develop into maturity to form retinal cells. Instead, these cells (retinoblasts) start to divide and grow out of control to form tumor known as retinoblastoma.
Although the exactly process of how cells start growing out of control is complex, but it almost always starts with genetic change of Retinoblastoma gene (RB1 gene). Retinoblastoma gene (RB1) gene helps to control development of retinoblasts to form retinal cells. Mutation to this gene, results into out of control growth of cells which may become cancer. Depending on when the cancer starts, retinoblastoma is of two kinds;
• Congenital (hereditary) retinoblastoma. Congenital means a baby is born with the disease or abnormality. In this form of retinoblastoma a baby is born with mutated RB1 gene in body cells. Most of children with this form of mutation do not have family history of the disease which means they did not inherit this mutation from parents but it occurred during early development in the womb. The reason for this is still unclear
Children born with RB1 gene mutation are likely to develop retinoblastoma in both eyes (bilateral retinoblastoma). With the possibility of having several tumors within the eye (multifocal retinoblastoma). Because all the cell in the body have mutated RB1 gene, these children will be at risk of developing cancer in other parts of the body. For example these children develop cancer in the pineal gland at the base of the brain (a pineoblastoma).
• Sporadic (non hereditary) retinoblastoma. In this form of retinoblastoma, a child does not inherit RB1 gene mutation from parents but it occurs on its own. These children normally have retinoblastoma in one eye (unilateral retinoblastoma) as mutation occurs only in one cell in one eye. These type of retinoblastoma are likely to be detected at later age than hereditary one. These children also are likely to have lower risk of other cancers compared to congenital ones.
Risk factors for retinoblastoma
When it comes to cancer, anything that increases your probability of developing cancer is called a risk factor. Risk factors only influence development of cancer but it does not directly cause cancer. Sometimes people with risk factors do not develop the disease while those with no risk factors do develop the disease. Knowing risk factors will help you live your life making some better healthy choices to reduce the risk. For most children with cancer, the underlying cause is unknown.
Even if your child has a risk factor, it does not mean they will develop cancer. Many children with a risk factor will never develop cancer, while others with cancer may have had no known risk factors. Even if a child with a risk factor develops cancer, it is usually hard to know how much that risk factor contributed to the development of their disease. The causes of retinoblastoma are not well understood, but factors associated with a higher chance of developing retinoblastoma include the following.
• Age. Retinoblastoma is a cancer for children (below 5 years). Hence being in that age is one of the risk factors for the disease.
• Family history (heredity). Retinoblastomas are due to a faulty RB1 gene. This faulty gene can run in families, or it may develop for the first time in the child during early developments in the womb. Although most cases of retinoblastoma do not run in families, a child in a family with history of this disease will be at slightly higher risk of developing the disease.
Prevention of retinoblastoma
To prevent something you need first to know what causes it. Retinoblastomas are due to genetic faulty (RB1 gene), hence the only way to prevent this cancer is to prevent mutation of RB1 gene. Unfortunately, the exact cause for mutation of that gene is still unknown hence preventing retinoblastoma becomes very difficult.
In addition to that, adult cancers differ from children cancers in that, adult cancers are highly linked to environmental and lifestyle factors such as smoking and obesity. However children cancers are not associated with such factors as children are not exposed to such factors and it takes a long time (years) for such factors to influence development of cancer. So even reducing the risk of developing cancer through avoiding such factors doesn`t work for retinoblastoma.
Early detection and screening of retinoblastoma
Early detection of cancer is very crucial as it improve prognosis (treatment outcome) of the disease. Early detection of some cancers has been greatly contributed by the process called screening.
Screening is the process of running some tests to someone with no signs and symptoms of the disease with the intention of testing for presence or absence of the disease. Unfortunately there are no widely recommended screening tests for retinoblastomas.
Although there are no recommended screening tests for retinoblastomas, most cases of these cancers are detected while still at an early stage. This has been through routine physical examination of child`s eyes either by a parent, relative or a doctor.
During children’s regular physical exams, doctors routinely check their eyes. Some of the things doctors look for include changes in how the eyes look (inside or outside), changes in how the eyes move, and changes in the child’s vision.
Also, parent or relative may notice that a young child’s eye doesn’t look normal, prompting a visit to the doctor. It’s important for parents to be aware of the possible signs and symptoms of retinoblastoma, and to report anything unusual to the doctor as soon as possible.
Signs and symptoms of retinoblastoma
Children with retinoblastoma may experience (have) some of the following signs and symptoms. Sometimes those signs and symptoms may be caused by other medical conditions other than retinoblastoma, so the only way you can find out is through seeing the doctor for more examination as soon as you realize that your child has one or some of those signs and symptoms.
1. Pupil (dark part at the center of the eye) appearing white instead of red when light is shone into it. This is also called white pupillary reflex.
2. Poor vision
3. Iris with different colours
4. Lazy eye. Eyes may seem to be looking in different directions. This is may be the result of weakness of eye muscles
5. Red and painful eye
6. Large than usual eyeball (bulging of the eye)
Diagnosis of retinoblastoma
Following suspicion of retinoblastoma, doctors use various tests to locate the disease, learn if the disease has spread to other organs of the body and some tests will help to determine stage of the disease. Before or during running those diagnostic tests to your child, among the things that your doctor will consider include the following;
• Results of previous tests
• General health condition of your child
• Type of cancer suspected
Among the diagnostic tests used when dealing with retinoblastoma, include the following;
1. Physical examination and medical history. The doctor will review child`s history for risk factors such as family history of the disease. The doctor will also do some physical examinations of the eye and if retinoblastoma is suspected, the child will be referred to an ophthalmologist (specialized doctor for eye diseases) for more examination. Ophthalmologist may use special light and magnifying lens to careful examine the eye.
2. Ultrasound. Ultrasound uses sound waves to generate picture of different parts of the body. A transmitter that emits sound waves is moved over the child’s body. A tumor generates different echoes of the sound waves than normal tissue does, that`s why, Ultrasonography is useful in distinguishing retinoblastomas from non-neoplastic conditions.
3. CT scan. Computed tomography scanner, uses x-rays to generate images of different organs of the body. This test is different from the normal x-ray imaging as CT uses x-rays to create many pictures of body parts from different angles, then computer combine these images to produce a detailed cross sectional images of your body parts.
CT scan is used to locate the tumor and show if tumor has spread to other parts of the body. Before scanning, you may be given a contrast that will make the images to be look clear. This can be given orally or through injection (intravenously).
1. MRI scan. Magnetic resonance imaging uses radio waves and strong magnetic field to generate picture of internal parts of the body. Magnetic resonance imaging is used to locate tumor and show if cancer has spread to other parts of the body.
Unlike CT scan, MRI uses magnetic field and radio waves to create images of body parts. Normally, either a CT or an MRI scan is needed, but usually not both. Because CT scans give off radiation, which might raise a child’s risk for other cancers in the future, most doctors prefer to use MRI.
However, a CT scan can show deposits of calcium in the tumor much better than an MRI, which can be very helpful when the diagnosis of retinoblastoma is not clear. You may be given a contrast before the scanning so as to produce a better detailed image.
• Bone scan. Bone scan is a nuclear medicine test that uses very small amount of radioactive substance called tracer. This is used to examine if retinoblastoma has spread to the bones (skull). During the test, small amount of radioactive tracer will be injected (intravenously), where the tracer will settle in high concentration to the bones with abnormality throughout the body. Special camera will be used to detect the radioactivity and show picture of the skeleton.
Staging of retinoblastoma
Staging is a standard way used by cancer care team to explain the location of tumor, size of the tumor and extent of spread of cancer. Staging also enables the oncology team to decide on the suitable treatment option. In this process of staging doctors normally use systems in order to describe the stage of cancer.
But for practical purposes, when determining the best treatment options for this cancer, doctors often divide retinoblastomas into 2 main groups:
• Intraocular retinoblastoma. In this tumor is still within the one or both eyes but has not spread to surrounding tissues or distant parts of the body.
• Extraocular retinoblastoma. This is when tumor has spread beyond the eye to the tissues around the eye or other parts of the body such as brain and bone marrow.
Treatment of retinoblastoma
Children cancers are not common, so even their management is normally slightly different from the way adult cancers are managed. This is way children cancers are treated in a specialized centers that deals with management of children cancers.
Children with cancers and their families have special needs and these needs can be met best by cancer centers for children, working closely with the child’s primary care doctor. These centers have teams of specialists who understand the differences between cancers in adults and those in children, as well as the unique needs of younger people with cancer.
Making treatment decision
Since a person with cancer is a child then treatment decision has to be made by the parents. With the help of a child`s doctor, parents have to take time to understand about the condition their child, treatment options and possible outcome of treatment. Parents are free to ask if there is anything they do not understand clearly for example any possible side effects of treatments.
Normally when making treatment plan, when it comes to treatment options, doctors normally provide treatment options basing on the following;
• Stage of the disease
• General health condition of a child
• Possible side effects
• Parent`s preference
Taking part in clinical trial
Clinical trials are new drugs or modified mode of treatment or new treatment combination for cases like yours that are to be tested if they are effective to be used as standard care treatment option or not. Your child`s doctor or nurse will discuss with you if you want your child to take part in clinical trial.
Over the years, trials have improved treatments and led to better outcomes to children cancers. It may be helpful to talk with another specialist to get second opinion before letting your child take part in clinical trials. And if you decide to take part, you can also withdraw at any time.
Treatment of retinoblastoma requires team of doctors (pediatric oncologists), nurses and other health care professionals. Also pediatric cancer centers normally have additional support services for children and their families, such as child life specialists, dietitians, physical and occupational therapists, social workers, and counselors. Most cases of retinoblastoma can be cured. In addition to curing the disease, the main goal for treatment is to preserve vision.
There are different treatment options for retinoblastoma that are used for different cases depending on the stage of the disease. Among those options, there are those that will preserve vision and those that won`t preserve. Ability to preserve or not preserve vision will also depend on the stage of the disease. Treatment options for retinoblastoma include the following;
Surgery is the treatment option that involve removing tumor and surrounding health tissues by operation. The procedure is carried out by a special trained pediatric ophthalmologist.
Surgery is preferred when there is no possibility of preserving vision. Surgery to remove the eye is called enucleation. Children with cancer in one eye are often cured with this option. If both eyes are affected and there is no possibility of preserving vision, then both eyes will be removed. Surgery treatment is done by a special trained pediatric ophthalmologist.
During the surgery, an implant is placed in the eye socket to take the place of the eye. This implant will be attached to the eye muscles so that it can move, and a life-like layer can be added to the surface to create an artificial eye, called prosthesis.
Side effects of surgery
One of the obvious side effect of enucleation is the loss of vision in that eye, although most often the vision has already been lost because of the cancer.
In addition to that, removing the eye can also affect the future growth of bone and other tissues around the eye socket, which can make the area look somewhat sunken although using an orbital implant can sometimes lessen this effect.
Radiation therapy is the use of high energy x-rays or other radiation particles to kill or destroy cancer cells. Radiation therapy is given by a specialized doctor known as radiation oncologist. For treatment of retinoblastoma, radiation therapy can be given as either external beam radiation therapy or brachytherapy.
• External beam radiation therapy. External beam radiation therapy involve aiming radiation to the tumor from the source (machine) positioned outside the body.
• Brachytherapy. This is also called internal radiation therapy. For treatment of retinoblastoma, a small metal disc called eye plaque will be loaded with radioactive material (seeds), then the disc is placed on the outside of the eye near the tumor for a few days.
Radiation therapy can sometimes be used as an alternative to surgery so that your child can still use their eye. Radiation therapy can have long-term side effects in children. If the potential benefits outweigh the risks and radiation therapy is included in your child’s treatment, special care will be taken to reduce these risks.
Side effects of radiation therapy
Possible side effects of radiation therapy, include those that will last for short period and those that will last for long. Among those that normally last for short period then go away following completion of treatment is;
Among those that would last for long include, interference of normal development of the body, including growth of the bones around the eye. Also there will be increased risk of additional tumors later in life for children with the hereditary form of retinoblastoma.
Chemotherapy is the treatment of cancer by using ant cancer drugs to destroy cancer cells. Chemotherapy is given by a specialized doctor known as pediatric oncologist. For treatment of retinoblastoma, chemotherapy is usually given as a combination of medicines to try to prevent the cancer cells from becoming resistant to just one or two medicines.
Side effects of chemotherapy
Side effects of chemotherapy depends on type of drug used, dose and how long those drugs have been used. Some of the side effects can go away on their own while others will require medications to relieve. Some of those possible side effects include;
• Loss of hair
• Nausea and/or vomiting
• Diarrhea or constipation
• Risk of infections due to low white blood cells
• Easily bruising and bleeding due to low platelets
• Fatigue (feeling tired) as a result of low red blood cells
• Mouth sores.
Cryotherapy is the treatment option that involve using liquid nitrogen to freeze and kill cancer cells. This treatment is also called cryosurgery or cryoablation. This kind of treatment is effective for small tumors on the front of the eye and is not used for those with several tumors.
During the procedure, a child will be put to sleep and the probe will be put on the outer surface of the eyeball next to the tumor. Tumor will then be frozen. This procedure is normally done for several times (normally 2-3 times).
Side effects of cryotherapy
Possible side effects of cryotherapy include causing damage to retina and causing eyelids to swell.