Responsiveness of retinoblastoma to local diaziquone. Studies in a xenograft model.

The benefits of chemotherapy in the management of early or bilateral retinoblastoma are doubtful and are difficult to study. A xenograft model has been developed in which the therapeutic response of retinoblastoma heterotransplanted to the anterior chambers of nude mouse eyes can be evaluated. Cyclophosphamide has been shown to be the most effective of the conventional agents. The new drug diaziquone was tested in the model against five patient-derived xenografted cell lines, using both systemic (intraperitoneal) and local (eye drops) methods of administration. A total of 359 xenograft tumors in 229 experimental animals were monitored after treatment with intraperitoneal cyclophosphamide, intraperitoneal diaziquone, or local diaziquone. Responses to all three regimens were demonstrated in each of the five xenograft lines. Diaziquone compared favorably with cyclophosphamide as systemically administered chemotherapy. Local diaziquone was as effective as intraperitoneal injection in producing tumor responses. It is suggested that methods for local administration of diaziquone may be adapted to the clinical setting, and that a role for this modality may be found in a combination of nonoperative approaches to the management of small, intraocular tumors.