Retinoblastoma

Retinoblastoma is a malignant tumor of childhood that arises in the retina of the eye. The majority of cases are diagnosed before the age of five years. The incidence of retinoblastoma is higher in developing countries than in Europe and the United States, where the age standardized annual incidence rate is about 4 cases per million. In some developing countries, the incidence rates per million may be two to six times higher (Figure 1) or even more, since very little information is available from rural areas, where retinoblastoma appears to be particularly common. About 20 to 30% of patients have bilateral disease. The disease may occur sporadically or it may be inherited. It is characterized by a rapid growth rate. When the disease is detected at early stages and confined to the eye, children have a good prognosis and the anticipated five-year disease-free survival rate (DFS) is 90% or greater. However, in children with disease that extends beyond the eye, particularly to distant parts of the body, the five-year DFS is poor, less than 10%. The percentage of children with extraocular disease (outside the eye) at diagnosis is much higher in developing countries (approximately 35 to 50%).

The child at left has leucocoria, also known as "cat's eye" or "white eye." The whitish appearance of the pupil is caused by the tumor in the eye, and is, with strabismus (squint), the most common early sign of the tumor. If not dealt with at this stage, when it is eminently curable, the tumor continues to grow and may become sufficiently advanced to make cure highly unlikely with presently available therapy—as illustrated by the case history presented on page 7.

The two most common early symptoms observed in children are leucocoria (cat's eye reflex) (Figure 2) and strabismus (squint). Other signs of the disease include redness of the eye, fixed pupil, or other more subtle changes. When the disease is more advanced, patients may experience swelling of the tissues around the eye, proptosis (protruding eye), or sunken eye. Change in or loss of vision may also occur, but this is difficult to assess in very young children. In addition to a detailed ophthalmologic (eye) examination performed while the patient is under anesthesia, special x-rays and ultrasound evaluations are used to establish the diagnosis.

Ophthalmologists, pediatric oncologists, and radiation oncologists are all essential members of the multi-disciplinary team needed to effectively treat patients with retinoblastoma. The goal of treatment is cure and preservation of sight. The therapeutic approach is dependent upon factors such as whether disease is unilateral or bilateral, the potential for vision, the size, location and number of lesions, and whether the disease has spread beyond the eye. Availability of treatment modalities as well as the expertise of a particular center in the management of patients with retinoblastoma are also important considerations. For small tumors within the eye, treatment consists of external beam radiation, photocoagulation (laser), or cryotherapy (precise freezing). When tumors are large or if there is little expectation that vision can be preserved, the eye is removed. The use of systemic chemotherapy to reduce tumor volume prior to a physical treatment modality to permit preservation of vision is currently under investigation in Europe, the USA, and many developing countries. The most common chemotherapy drugs used for chemoreduction are carboplatin, vincristine, and etoposide. In patients with extraocular disease, particularly those with spread to the central nervous system or bone marrow, chemotherapy is the primary component of treatment. - Melissa Adde