Treatment of Extraocular Retinoblastoma

In the United States, a minority of patients with retinoblastoma presents 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. In patients with the genetic form of retinoblastoma, central nervous system (CNS) disease is less likely the result of metastatic or regional spread than another primary intracranial focus, such as a pineoblastoma, associated with the trilateral retinoblastoma syndrome.

There is no clearly proven effective therapy for the treatment of extraocular retinoblastoma. Clinical trials are now under way to improve the overall dismal outcome (survival of approximately 10%) for this group of patients. Those with CNS metastases appear to do worse than those with other forms of extraocular disease. In the past, chemotherapy has included conventional doses of vincristine, cyclophos-phamide, and doxorubicin, and, although they produce an initial response, relapse is common. Carboplatin, ifosfamide, and etoposide have shown more promise for remission and a regimen similar to that used for relapsed Wilms' tumor (see Chapter 19, page 556) can be employed. Other induction regimens include the use of cisplatin or carboplatin together with etoposide, cyclophosphamide, and vincristine. There is no recommended standard regimen, and it is largely based on institutional preference. Generally, induction chemotherapy is given for four cycles and this is followed by high-dose chemotherapy followed by stem cell rescue. Following recovery from stem cell transplantation, radiotherapy is generally given to sites of initial bulky disease. As with induction regimens, there is no standard stem cell transplant regimen. A regimen using etoposide, carboplatin, and melphalan such as that used to treat relapsed Wilms' tumor (see Chapter 19, pages 556-557) is used by some centers. Others use regimens of carboplatin, thiotepa, and etoposide or carboplatin, etopo-side, and cyclophosphamide or carboplatin, thiotepa, and topotecan (Table 23-5).

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