Radiation Therapy in Retinoblastoma

Abstract

Retinoblastoma is a rare, congenital, malignant tumor which predominantly affects infants and young children. Approximately 65 per cent of the cases are unilateral, are generally far advanced in the globe when first seen, and are treated by enucleation (5). In 35 per cent, tumors are found in both eyes, either simultaneously or within a short time of each other; in these, it is usual to enucleate the more severely affected eye because it is unlikely that useful vision can be maintained and to irradiate the less involved eye in an attempt to preserve sight. A smaller group of cases, those with early unilateral or bilateral disease, are also treated with radiation (6). In addition, irradiation is given for postoperative residual or recurrent disease and as a palliative measure for distant metastases. Although excellent studies are available, assessing the survival results and genetics of retinoblastoma, none has analyzed the local control rate due to radiation therapy, the effect of currently employed radiation doses on subsequent vision, and the efficacy of more than one course of irradiation for recurrent disease (2, 3, 10, 11). Furthermore, the effect of the alkylating agent triethylene melamine (TEM) , used in conjunction with radiotherapy, on control rates is not known. In order to clarify these points, we have analyzed the charts of all children with retinoblastoma seen at the Institute of Ophthalmology, Columbia-Presbyterian Medical Center, and treated with radiation from Jan. 1, 1954 to Dec. 31, 1963. Two hundred thirty-six patients were registered during these ten years. Six have been excluded from consideration because the stage of disease at the time of initial treatment elsewhere could not be determined. The sex and age occurrence for the remaining 230 patients is shown in TABLE 1. Thirty-three patients had post-operative residual or recurrent disease in the orbit following enucleation. Fourteen of these 33 also had disease in the opposite intact globe and will, therefore, be considered in both the residual and the primary globe irradiation categories. Twelve received radiation therapy to both eyes. Thus, a total of 223 eyes were treated. Only 6 patients had localized unilateral disease treated with radiation. The extent of disease in each eye was grouped (staged) according to the system of Reese and Ellsworth (TABLE II) (6,7). The principal variables in treatment have been (a) the radiation quality (kilo-voltage vs. supervoltage), (b) the dose/time relationship, (c) the withholding or use and route of administration of TEM, and, more recently, (d) the addition of photocoagulation to the therapy of this disease. Prior to 1958, the two-field technic (ipsilateral temporal and contralateral oblique nasal) of Martin and Reese was employed (8).