Retinoblastoma is a malignant tumor that affects the retina at the back of the eye.
It is the most common cancer of the eye in children.
As a rule, children under 5 years of age are affected, very rarely it occurs in adults.
In most children with retinoblastoma, the disease affects only one eye. However, one in three children develops cancer in both eyes.
The most common sign of retinoblastoma is a visible reflex in the pupil, also called leukocoria (cat’s eye reflex).
This unusual white reflection is particularly evident in photographs taken with flash.
Annually, about 1 in 20,000 newborn children in the United States develops retinoblastoma.
Retinoblastoma accounts for about 3 percent of all malignant tumors in childhood.
How does retinoblastoma develop?
The eyes develop very quickly as long as the children are still in the uterus:
- In the early stages of development, the eyes have cells called retinoblasts that divide into new cells to fill the retina.
- At a certain point, the cells stop dividing and become mature retinal cells.
- In rare cases, some retinoblasts continue to grow rapidly and uncontrollably, rather than developing the special cells that receive the light, forming the cancer known as retinoblastoma.
The chain of events leading to retinoblastoma is complex, but begins with an abnormality (mutation or modification) of a tumor suppressor gene called retinoblastoma protein (RB or RB1).
The normal RB1 gene blocks the uncontrolled growth of cells because it acts on the cell cycle.
This gene is located on the band q14 of chromosome 13 (abbreviation 13q14).
Depending on the change that occurs in the RB1 gene, 2 different types of retinoblastoma can form.
Hereditary retinoblastoma As a rule, this type of tumor occurs at a younger age than non-hereditary retinoblastoma
Bilateral retinoblastoma is usually hereditary, while unilateral retinoblastoma is non-hereditary.
Genetic mutations that increase the risk of retinoblastoma and other tumors can pass from parents to children.
Hereditary retinoblastoma passes from parents to children according to a dominant autosomal pattern:
- This means that a single copy of a parent’s mutated gene is enough to increase the risk in the children.
- If one parent has a mutated gene, each child has a 50% chance of inheriting that gene.
Sporadic retinoblastoma (non-hereditary)
In most children, retinoblastoma is not hereditary.
About 40% of children born with this defect have inherited this gene from a parent.
In about 60% of cases, gene variation still develops in the uterus.
Since all cells in the body have the modified RB1 gene, there is an increased risk of developing other tumors outside the eye in this condition.
In particular, the following developments are more likely:
- Some children with this form of retinoblastoma develop a tumor on the pineal gland of the base of the brain (pinealoblastoma). This is also called trilateral retinoblastoma
- A type of bone tumor called osteosarcoma.
- Tumors in soft tissue, for example, in muscles.
- An aggressive cancer of the skin and eye, called melanoma.
Sporadic retinoblastoma develops in just one eye. It is not known what causes the mutation of the RB1 gene.
A child with sporadic (non-hereditary) retinoblastoma develops the tumor in just one eye.
This type of retinoblastoma often occurs at a later age than the hereditary form.
Classification of retinoblastoma
- Intraocular retinoblastoma is found in one or both eyes, but it does not extend beyond the eyes.
- In extraocular retinoblastoma, the cancer has spread beyond the eye to surrounding tissues or to other parts of the body, such as the brain, spinal cord, bone marrow or lymph nodes.
Stages of retinoblastoma according to the International Classification of Retinoblastoma (ICRB)
Intraocular retinoblastoma is divided into four stages:
- Phase I: The tumor is confined to the retina.
- Phase II: The tumor is confined to the eyeball.
- Phase III: The tumor spreads to areas around the eye.
- Phase IV: The tumor spreads via the optic nerve to the brain or has metastasized to soft tissue, bone or lymph nodes via the bloodstream.
How can you recognize it? Signs and symptoms of retinoblastoma
The first sign of retinoblastoma is a white pupil, which may appear silvery or yellow in full light. This formation is called leukocoria.
Other symptoms include:
- strabismus (strabismus),
- Reddened, often painful pupil,
- pupil and eyeball that appear larger than normal,
- iris of a different colour,
- Reduction or loss of vision until blindness.
Diagnosis of retinoblastoma
Early diagnosis of retinoblastoma may mean that the child needs less intensive therapy.
The ophthalmologist examines the eye under anesthesia. Retinoblastoma can only be diagnosed by clinical examination of the eye, usually no biopsy is performed.
There are examinations to determine the position and size of the tumor. In addition, it must be checked whether a spread into the surrounding structures has begun.
Possible investigations are:
- Echography. This is a painless examination that uses sound waves to examine the eye and surrounding structures.
- Magnetic resonance imaging. This study uses magnetic fields to create a detailed picture of the eye and head.
- The doctor inserts a fine needle between the bones of the lower spine to take a sample of cerebrospinal fluid. The fluid is examined microscopically to determine if tumor cells are present in it.
- Biopsy from the bone marrow. It is performed to determine whether tumor cells are located in the bone marrow.
- Bone scintigraphy. A series of X-rays is used to check whether there are signs of the cancer spreading to the bones.
- Blood test. This examination is carried out in order to carry out the genetic test of the RB gene. The results of this investigation may not be available until months later.
- Eye examination with dilated pupil.
My son was diagnosed with retinoblastoma. Should I also have my other children examined?
Some cases can be hereditary, so all siblings of the affected child should be examined to rule out this disease in them.
What is the probability that the next child will have the same condition?
The possibilities can vary from 1 in 15,000 to 45% and depend on many factors, including familial predisposition to retinoblastoma, if the tumor affects both eyes, etc.
Treatment of retinoblastoma
Ophthalmologist and oncologist work together in the treatment of a child with retinoblastoma.
This team puts together an individual treatment plan for each patient, depending on the spread of the disease inside the eye, whether one or both eyes are affected and whether there is a spread beyond the eye.
There are many types of treatment for retinoblastoma, all of which have the goal of killing the tumor cells.
The following treatments may be prescribed:
- Systemic chemotherapy: Drugs that kill the tumor are given orally or intravenously by injection.
- Intra-arterial chemotherapy: In some cases, doctors inject the chemotherapy drugs directly into the blood vessels that supply the eye so they can act directly on the tumor.
- Radiotherapy with external radiation: the rays are precisely focused on the tumor to kill the tumor cells.
- Brachytherapy: This is a type of internal radiation therapy in which the radioactive material (capsule) is placed inside the tumor to concentrate the radiation on specific areas. This form of treatment minimizes the damage to the healthy surrounding tissues.
- Radiation carrier: A disc with a contained radiation dose is placed directly on the tumor.
- Cryotherapy: Liquid nitrogen or argon gas, two extremely cold substances, are used to freeze and destroy the diseased tissue.
- Transpupillary thermotherapy: Laser energy heats the tumor cells and surrounding blood vessels to kill the cancer cells.
- Photocoagulation: Laser energy is directed to blood vessels and leads to the formation of blood clots, which deprive the tumor cells of nutrients.
- Enucleation: In severe cases of retinoblastoma (very rare), the entire eyeball is removed to prevent the cancer cells from spreading to other areas of the body. Instead of the removed eyeball, an ocular prosthesis (vitreous eye) can be inserted.
What are the life expectancies of retinoblastoma?
Although retinoblastoma is a dangerous condition, it is rarely fatal if treated appropriately.
With the right and early treatment by an experienced ophthalmologist, the cure rate of patients is 95%.
The prognosis depends on the following factors:
- Severity of the disease.
- Size and location of the tumor.
- Presence or absence of metastases.
- Response of the tumor to therapy.
- Age and general health of the child.
- Sensitivity of the child to special medications, procedures or therapies.