125I embedded in an orbital prosthesis for retreatment of recurrent retinoblastoma

The application of radiation therapy in the retreatment of unilateral recurrent retinoblastoma presents a very difficult dilemma in which consideration must be given to preservation of vision in the remaining eye while tumoricidal doses of irradiation are delivered. A technique is described in which a methylmetraculate eye sphere carrying a single Iodine-125 seed was used to deliver local irradiation to the orbital tissues in a patient with multiple episodes of recurrent retinoblastoma. The tissue dose at 2 mm depth was 2630 cGy while the dose to the retina of the remaining eye and to the optic chiasm was negligible.