In developed 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 occur into the brain and meninges with subsequent seeding of the spinal fluid, as well as distant metastatic disease involving the lungs, bones, and bone marrow.
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; lymphatic, hematogenous, and central nervous system (CNS) metastases occur in the remaining patients. Treatment should include systemic chemotherapy and radiation therapy; with this approach, 60% to 85% of patients can be cured. Since most recurrences occur in the CNS, regimens using drugs with well-documented CNS penetration are recommended. 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, it is recommended that surgery is delayed until response to chemotherapy has been obtained (usually two or three courses of treatment). Enucleation should then be performed and an additional four to six courses of chemotherapy administered. Local control should then be 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 should also receive similar systemic treatment, and irradiation should include the entire orbit (36 Gy) with 10 Gy boost to the chiasm (total 46 Gy).
Central nervous system disease
Intracranial dissemination occurs by direct extension through the optic nerve and its prognosis is dismal. Treatment for these patients should include platinum-based intensive systemic chemotherapy and CNS-directed therapy. Although intrathecal chemotherapy has been traditionally used, there is no preclinical or clinical evidence to support its use. Although the use of irradiation in these patients is controversial, responses have been observed with craniospinal irradiation, using 25 Gy to 35 Gy to the entire craniospinal axis and a boost (10 Gy) to sites of measurable disease. Therapeutic intensification with high-dose marrow-ablative chemotherapy and autologous hematopoietic progenitor cell rescue has been explored, but its role is not yet clear.[Level of evidence: 3iiA]