In high-income countries, few patients with retinoblastoma present with extraocular disease. Extraocular disease may be localized to the soft tissues surrounding the eye or to the optic nerve beyond the margin of resection. However, further extension may progress into the brain and meninges with subsequent seeding of the spinal fluid and as distant metastatic disease involving the lungs, bones, and bone marrow.
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Orbital retinoblastoma occurs as a result of progression of the tumor through the emissary vessels and sclera. For this reason, transscleral disease is considered to be extraocular and should be treated as such. Orbital retinoblastoma is isolated in 60% to 70% of cases.
Treatment includes systemic chemotherapy and radiation therapy; with this approach, 60% to 85% of patients can be cured. Because most recurrences occur in the central nervous system (CNS), regimens using drugs with well-documented CNS penetration are used. Different chemotherapy regimens have proven to be effective, including vincristine, cyclophosphamide, and doxorubicin and platinum- and epipodophyllotoxin-based regimens, or a combination of both.[1,2,3]
For patients with macroscopic orbital disease, delay of surgery until response to chemotherapy is achieved (usually two or three courses of treatment) has been effective. Patients then undergo enucleation and receive an additional four to six courses of chemotherapy. Next, local control is consolidated with orbital irradiation (40 Gy to 45 Gy). Using this approach, orbital exenteration is not indicated.
Patients with isolated involvement of the optic nerve at the transsection level are considered to have extraocular disease and are treated using systemic therapy, similar to that used for macroscopic orbital disease, and irradiation of the entire orbit (36 Gy) with 10 Gy boost to the chiasm (total of 46 Gy).
Standard treatment options for extraocular retinoblastoma (CNS disease) include the following:
Systemic chemotherapy and CNS-directed therapy.
Systemic chemotherapy followed by myeloablative chemotherapy and stem cell rescue.
Intracranial dissemination occurs by direct extension through the optic nerve, and its prognosis is dismal. Treatment for these patients includes platinum-based intensive systemic chemotherapy and CNS-directed therapy. Although intrathecal chemotherapy has been used traditionally, there is no preclinical or clinical evidence to support its use. The administration of radiation therapy to these patients is controversial. Responses have been observed with craniospinal radiation using 25 Gy to 35 Gy to the entire craniospinal axis and a boost (10 Gy) to sites of measurable disease.