Retinoblastoma (Rb) is a rare form of cancer that rapidly develops from immature cells of the retina. It is a malignant Cancer of the eye, found exclusively in young children below 7 years of age. In 75% of cases, the tumor is found only in one eye, while the rest 25% cases report tumor in both eyes.
Retinoblastoma is usually confined to the eye but, if left untreated, is capable of metastasis or spreading to other parts of the body. The tumor is highly curable if its growth is restricted to the eyes only, the outlook declines with the increase in the spread of the Cancer cells.
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Occurrence Rate of Retinoblastoma Cancer
Retinoblastoma is a rare disease and is indicated by a white dot on the retina and a squint. It accounts for almost 2% of all cancer occurrences in children below the age of 15. Globally, there are 11 cases per million children below 5 years of age, who have retinoblastoma. It may relieve the mind of many to know the rarity of this disease.
However, a recent survey by AIIMS revealed that the occurrence rate of Retinoblastoma among Indian children is rapidly increasing. Statistics suggest that almost 20,000 new cases of the disease are reported every year. 9-10 % of all Pediatric Cancer patients in India have Retinoblastoma. Though the incidences are increasing at an alarming rate, yet it can be cured when detected early. Median age at diagnosis was 2 years for boys and 1 year for girls with unilateral retinoblastoma; it is less than 12 months for bilateral disease.
For a country of 3120 crores, the number of cases reported might seem small when compared with breast cancer or other head and Neck cancer. Hence, opening with such information puts it in proper perspective.
The Retina is a thin layer of tissues at the back of the eyeball that contains cells sensitive to light. It is the light-detecting tissue of the eye.
- The retina receives the light focused by the lens.
- It converts the light into neural signals and sends these signals to the brain for visual recognition.
How does Retinoblastoma Cancer develop?
A baby’s eyes start developing in the womb early in the first trimester of pregnancy. Retina i.e the light detecting part of the eye is formed by rapidly growing cells called Retinoblasts. These growing cells eventually mature to form the retina. In some rare scenario, the growth of retinoblast cells goes on abnormally forming a tumor in the eye.
These tumors may continue to grow, filling almost the entire vitreous humor (the jellylike substances the fills the eyeball). These tumors can also break off and spread to other parts of the eye, and eventually to other distant organs of the body.
Types of Retinoblastoma Cancer
- Congenital (hereditary) Retinoblastoma:
For about 33% of children with Retinoblastoma, the abnormality in the RB1 gene is present at birth and is in all the cells of the body, including all the cells of both retinas. This is known as a germline mutation.
In most of these children, there is no family history of this Cancer. Only about 25% of the children born with this gene change inherit it from a parent. Children born with a mutation in the RB1 gene usually develop retinoblastoma in both eyes (known as Bilateral Retinoblastoma), and there are often several tumors within the eye (known as multifocal retinoblastoma).
- Sporadic (non-hereditary) Retinoblastoma
In about 66% of children with Retinoblastoma, the abnormality in the RB1 gene develops on its own in only a cell in one eye. The causes of this change are still under scrutinization. A child who has sporadic retinoblastoma develops only one tumor in one eye. This type of Retinoblastoma is often found at a later age than the hereditary form.
Children with this type of Retinoblastoma do not have the same increased risk of other Cancers as children with congenital Retinoblastoma.
- Leukocoria (cat’s eye reflex or white pupil). This may be first observed in photographs where the eye appears white rather than reflecting the reddish-orange light from the eye’s retina.
- Leukocoria Misaligned eyes (strabismus)
- Blurred vision
- Squint, eyes appear to be looking in different directions (lazy eye).
- Redness or inflammation of eyes
- Infection around the eye.
- The eyeball is larger than normal.
- The colored part of the eye and pupil look cloudy.
A risk factor is anything that affects a person’s chance of getting a disease such as cancer. There are very few known risk factors for Retinoblastoma.
Age: Most children diagnosed with retinoblastoma are younger than 3 years old. In most cases, hereditary retinoblastomas are found during the first year of life, while non-inherited Retinoblastomas tend to be diagnosed in 1- and 2-year-olds. Retinoblastomas are rare in older children and in adults.
Heredity: 40% of Retinoblastoma patients have a genetic defect that leads to multiple tumors in one eye or both eyes. This is known as hereditary or germline retinoblastoma. These patients are typically diagnosed before 1 year of age. Patients with hereditary Retinoblastoma may pass this disease to their children.
Gender: It is more common in boys than girls.
Non Heredity: 60% of patients have a nonhereditary form of retinoblastoma. Each of these patients develops a tumor in only one eye. Nonhereditary patients are diagnosed on average around 2 years of age.
Since the causative and risk factors for Retinoblastoma are all natural and we have no control over them, so it becomes almost impossible to prevent the occurrence of Retinoblastoma Cancer. However, it brings a sigh of relief to know that the success rate of treatment is quite high when the cancer is diagnosed at its early stage. So the best prevention is through early detection.
General eye exam of the eyes of babies at birth and after 6 -12 months helps in detecting any serious congenital problems. Adults are advised to take their babies for a regular eye examination at least once a year or more often if one has any eye issues.
It is very important to stage Cancer for a planned diagnostic and treatment of the disease. Cancer is staged based on the size and location of the tumor(s). Although currently there are several staging systems available, the most convenient method is staging by the location of tumor.
- Intraocular Retinoblastoma: Cancer is found in one or in both eyes, but does not extend beyond the eye.
- Extraocular Retinoblastoma: Cancer has extended beyond the eye, usually through the optic nerve. It may be confined to the tissues around the eye, or it may have spread to other parts of the body.
- Trilateral Retinoblastoma: In Bilateral Retinoblastoma, a related tumor develops in the pineal gland at the base of the brain. The presence of these tumors can result in other neurological symptoms and require neuroimaging of the brain for diagnosis.
- Recurrent Retinoblastoma: Recurrent disease means that cancer has come back or progressed after it has been treated. It may recur in the eye or elsewhere in the body.
Another most common staging system for Retinoblastoma based on the size and spread of cancer is given below:
Stage 0: The tumor is in the eye only. The eye need not be removed and the tumor can be treated without surgery.
Stage I: The tumor is in the eye only. The eye needs to be removed and no cancer cells remain.
Stage II: The tumor is in the eye only. The eye needs to be removed, yet there are cancer cells left that can be seen only with a microscope.
- In stage IIIa, cancer has spread from the eye to tissues around the eye socket.
- In stage IIIb, cancer has spread from the eye to lymph nodes near the ear or in the neck.
- In stage IVa, cancer has spread to the blood but not to the brain or spinal cord. One or more tumors may have spread to other parts of the body such as the bone or liver.
- In stage IVb, cancer has spread to the brain or spinal cord. It also may have spread to other parts of the body.
The survival rate depends on several factors, including whether the Cancer has spread from the eye to other parts of the body.
- If the tumor is contained within the eye (one or both eyes), more than 95 percent of treated patients can be cured.
- For children with retinoblastoma in both eyes, about 70 to 80 percent of the eyes can be saved.
Retinoblastoma Cancer might be indicated by several symptoms like pain, fatigue or a lump. In case any of these signs are visible it is recommended to visit a doctor and go for an examination.
- Eye exam:
- Ophthalmoscopy: The inside of the eye is carefully observed using a small magnifying lens and a light to check the retina and optic nerve.
- Slit-lamp biomicroscopy: The retina, optic nerve, and other parts of the eye are checked thoroughly using a strong beam of light and a microscope.
- Fluorescein angiography: In this procedure, blood vessels and the flow of blood inside the eye is observed. An orange fluorescent dye called fluorescein is injected. As the dye travels through blood vessels, a special camera takes pictures of the retina and choroid to find any blockage or leakage.
- Blood test: A laboratory test in which a sample of blood or tissue is tested for a change in the RB1 gene.
- Ultrasound exam of the eye: In this procedure, high-energy sound waves are bounced off the internal tissues of the eye to make echoes. Eyedrops are used to numb the eye and a small probe that sends and receives sound waves is placed gently on the surface of the eye. The echoes make a picture of the inside of the eye and the distance from the cornea to the retina is measured. The picture, called a sonogram, shows on the screen of the ultrasound monitor.
- MRI (magnetic resonance imaging): In this procedure, a magnet, radio waves, and a computer are used to make a series of detailed pictures of the eye. This procedure is also called nuclear magnetic resonance imaging (NMRI).
- CT scan (CAT scan): In this procedure, a series of detailed pictures of the eye are taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called
The treatment depends on the number, position and size of the tumors in the eye. The aim of treatment is first to get rid of the cancer and secondly to try to protect the eyesight. Some treatments may cause changes in the vision in the affected eye.
Different types of treatment are available for patients with retinoblastoma. Some treatments are standard (the currently used treatment), and some are being tested in clinical trials.
Local Therapy: For smaller tumors, treatment is given to the eye itself. One of the following methods may be used:
- Cryotherapy/Focal Therapy: It is the treatment with laser therapy or freezing treatments (cryotherapy) while under anesthesia. These focal therapies may continue even after chemotherapy is complete. Sometimes, the tumors in the eye are small enough to be treated with only focal therapy.
- Laser Therapy: A laser is directed through the pupil and used to heat the tumour. A number of sessions of laser therapy are recommended at intervals of 3 to 4 weeks.
- Plaque: A small radioactive disc is stitched over the tumor on the outside of the eye. The disc needs to stay in place for up to four days while the radiation destroys the cancer cells.
- Thermotherapy: This process uses heat to destroy the cancer cells and may be combined with chemotherapy or radiotherapy, as heat can improve the effectiveness of these treatments. The heat is produced by a laser, which is directed at the tumor.
Anti-Cancer drugs are used to destroy Cancer cells. It may be given before the local treatments mentioned above, to help shrink the tumor and make treatment more successful. Chemotherapy can also be used if cancer has spread to other parts of the body, or if there’s a risk that it may spread. The chemotherapy drugs most commonly used to treat Retinoblastoma are carboplatin, etoposide and vincristine. Some of the most common chemotherapies used are:
- Systemic chemotherapy
- Regional chemotherapy
- Ophthalmic artery infusion chemotherapy
- Intravitreal chemotherapy
- Enucleation (Surgery)
If the tumor is very large and the vision in the eye is lost, an operation to remove the eye is recommended. The specialist will only do this if it is absolutely necessary. An artificial eye is then fitted.
Radiotherapy treats Cancer by using high-energy rays from a machine to destroy the Cancer cells while doing as little harm as possible to normal cells. It can be given to the whole eye but does have some effect on the surrounding tissue. Radiotherapy for Retinoblastoma is normally only used when other treatments have not worked well.
Retinoblastoma is a very rare disease having a high curative rate. When detected at an early stage it can be cured with surgery, chemotherapy, focal therapy and radiation without causing much harm to the eyes.
In case of experiencing any of the mentioned symptoms or having a familial history of Retinoblastoma Cancer, a complete diagnostic is recommended once in a year.
The age of the patients is generally very low, so the parents and relatives should take responsibility to keep a vigilant eye on the child’s behavior and consult the doctor in case of any suspicion.
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