Retinoblastoma

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at August 4, 2016
StartDiseasesRetinoblastoma

Retinoblastoma is a form of eye cancer that develops in the retina. 'Retino' refers to the retina, while blastoma refers specifically to the immature cells from which the cancer develops. Although it is a rare form of cancer, retinoblastoma is known as the most common form of cancer of the eye that develops in children.

Contents

Definition & Facts

The retina is a layer of tissue that is located at the innermost part of the eye. It consists of cells that are sensitive to light, which is received through the two other inner parts of the eye: the iris and the lens. The iris controls the amount of light that goes to the retina, while the lens focuses it on the retina.

The photoreceptor cells that comprise the retina connect to the optic nerve, which travels out the back of the eyeball to the brain to register the pattern of light it received. The brain then registers the pattern of light as images, thus enabling vision.

When a baby develops in the womb, the eyes contain retinoblasts, which are cells that divide into new cells; they stop dividing when they fill the retina. On the other hand, when they continue to divide without stopping, that process becomes retinoblastoma. 

Symptoms & Complaints

Since retinoblastoma is rare and usually affects small children, signs or symptoms are rarely observable. However, the most obvious and common sign of retinoblastoma is leukocoria, which is the medical term for the appearance of a white circle in the pupil, or the eye’s center circle. This is easily detected when light shines in the eye, particularly when taking pictures (thus the alternate terms “white eye” or “cat’s eye”).

In some cases, the person with this type of eye cancer might develop eyes that appear to be looking in different directions: a condition medically known as strabismus. Halted or slow eye development can also be a sign; conversely, it could be an enlarged eye that indicates retinoblastoma. Other common indicators include eye swelling, eye redness, and eye irritation

Causes

A risk factor for retinoblastoma is heredity. Continued growth in the number of the eye’s retinoblasts is typically attributed to a mutation in the gene known as the retinoblastoma protein or RB1 gene. This gene is present in all the cells in the developing baby’s body. While 25% of cases involve the genetic mutation being inherited from one of the parents of the child, it is otherwise caused by a mutation that spontaneously occurs during the early stages of development in the womb.

Hereditary retinoblastoma is usually distinguished from the non-hereditary kind by the number of eyes affected and the likelihood of passing the disease on from one generation to another. Both eyes affected indicates heredity, and the child has an increased risk of passing retinoblastoma to his or her progeny. On the other hand, just one eye affected means that it is non-hereditary, and the child is less likely to pass it on to his or her offspring.

Typically, children diagnosed with retinoblastoma tend to be no older than three years of age. Most hereditary cancers appear or are discovered within the child’s first year, while non-hereditary cancers usually occur after the first year of life. The older the child, the less likely retinoblastoma is to occur. 

Diagnosis & Tests

Retinoblastoma can be diagnosed during any regular physical check-ups during the child’s first months of life. The doctor can conduct a comprehensive eye examination by looking for any structural abnormalities. This can include the Hirschberg test to determine whether the child has strabismus by shining a light into each cornea.

Also available is the ophthalmoscope, which is an instrument that the doctor can use to look through the pupil. The ophthalmoscope searches for and finds the normal reddish-orange reflection from the eye’s retina to ensure ocular alignment. To make sure that the eye examination is thorough, the doctor might have to use anesthetics to keep the child still; this helps tremendously in making a positive diagnosis.

If the doctor finds an abnormality, he or she can carry out further testing, since such irregularity does not necessary indicate the presence of retinoblastoma. Indeed, signs or symptoms may point to an entirely different ailment. For instance, leukocoria may be caused by Coats’ disease. Thus, further testing is necessary.

Further testing usually involves imaging tests such as ultrasound, magnetic resonance imaging (MRI), and computed tomography (CT) scans. MRI and CT are helpful in conclusively defining the abnormality, while ultrasound is instrumental in defining the tumor’s height and thickness.

In some cases, once the doctor has made the diagnosis, he or she may refer the child to a specialist in treating cancer: known as an oncologist—or, more specifically, a pediatric oncologist. Surgeons and genetic counselors are also healthcare professionals who commonly receive such referrals. 

Treatment & Therapy

There are various approaches to treating retinoblastoma. However, the treatment choice is based on the tumor’s location and size, whether it has metastasized (spread to other areas of the body), the parents’ preferences, and the affected child’s overall health. The ideal treatment should take into account the ability to save the child’s life and vision, as well as to minimize any complications or side effects that are likely to occur.

Chemotherapy is the most common form of treatment, since it is useful for addressing tumors that have spread outside the eye. Also, there are different forms of chemotherapy according to the specific need. For instance, the oncologist may recommend systemic chemotherapy for tumors that have metastasized.

Other forms of treatment are often used with chemotherapy to aid in eliminating the remaining tumors. Prime examples include radiotherapy, which uses high-energy beams; thermotherapy, which uses extreme heat; and cryotherapy, which uses extremely cold substances. 

Prevention & Prophylaxis

Retinoblastoma has no known avoidable causes or risk factors. However, people who have had the disease can meet with a genetic counselor to determine the likelihood of passing the RB1 gene onto their children.