What is retinoblastoma?
Retinoblastoma is a malignant tumor that starts in the cells of the retina (the part of the eye responsible for sight). These cells multiply in a disorganized way and affect one or both eyes.
It is the most common childhood intraocular tumor – usually occurring before the age of 5 – and accounts for 2.5 to 4 percent of all pediatric cancers.
Two-thirds of cases are diagnosed before the age of 2 and 95% before the age of 5. This is directly related to laterality and delay in diagnosis. Patients with bilateral disease (in both eyes) are usually diagnosed before their first birthday, while those with unilateral disease (in only one eye) learn of the condition between the second and third year of life.
The two forms of retinoblastoma presentation are:
- Bilateral or multifocal, hereditary, corresponding to 25% of all cases – characterized by the presence of germline mutations of the RB1 gene (which can be inherited from an affected family member in 25% of the cases, or the result of a new germline mutation in 75%); and
- Unilateral or unifocal, corresponding to 75% of all cases – 90% of them are not hereditary and are considered sporadic, and the remaining 10% are germline.
In Brazil, retinoblastoma affects 1 in every 20 thousand live births, which corresponds to twice the incidence registered in the United States and in European countries.
Symptoms and signs of retinoblastoma
The main sign of the presence of retinoblastoma is leukocoria, a glowing reflection in the diseased eye, similar to the glow of cats’ eyes lit up at night. This is the reflection of light on the surface of the tumor itself, and is often only noticed in some eye positions, in artificial light, or in photos, when the light from the flash hits the eyes.
The child may also go blinky, have pain and swelling in the affected eye, or lose sight in the affected eye, and have photophobia (exaggerated sensitivity to light).
Diagnosis of retinoblastoma
After symptoms are noticed, the child should be examined by a doctor to seek a diagnosis. A fundus examination is done, with a well dilated pupil. Biopsies are not usually taken.
The patient undergoes a genetic counseling study to identify if the case is hereditary.
Additional imaging studies help in the diagnosis. Among the tests are two-dimensional ultrasound, computed tomography, and magnetic resonance imaging. They are important for checking the extraocular extension and differentiation from causes of leukocoria other than retinoblastoma.
Classifying the extent of the tumor at presentation is critical to recognize the prognosis, define the treatment, and assess the chances of cure.
The treatment strategy is always in the sense of saving life and preserving sight. The factors that need to be considered for tumors of all sizes are the laterality of the disease, the potential for preserving sight, and the intraocular and extraocular staging, i.e. how extensive and how severe it is.
Small retinoblastoma tumors can be treated with special methods that allow the child to continue to see normally. In these cases that are in the early stage, surgery is not performed, only methods that resemble laser and radiotherapy.
More advanced cases may undergo different therapeutic approaches. Possible ones are:
- Enucleation surgery (surgical technique to remove the mass without dissecting the eyeball);
- Local treatments, such as laser therapy and cryotherapy, combined with chemotherapy;
- Intravitreal and intra-arterial chemotherapies;
- Intravenous chemotherapy;
- Autologous bone marrow transplantation.
There is no way to prevent the appearance of retinoblastoma. In families with a history of the disease and of the presence of the RB1 gene, special attention should be paid to the symptoms, so that the child can be taken to the doctor as soon as possible, if necessary, and it is possible to preserve the child’s sight. Early diagnosis is essential.