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Abstract
In vitro x-ray survival experiments were performed on fibroblast strains derived from nine patients with sporadic unilateral retinoblastoma, 26 patients with hereditary retinoblastoma, and six normal controls. The x-ray sensitivity of the strains derived from the sporadic retinoblastoma patients and normal controls did not significantly differ from one another. The fibroblast strains derived from patients with hereditary retinoblastoma were significantly more radiosensitive to killing by x-rays as measured by clonogenic survival than either the sporadic strains or the strains derived from normal controls. We hypothesize that the increased in vitro radiosensitivity observed in some hereditary retinoblastoma strains is a reflection of an as yet uncharacterized defect in DNA or DNA replication postirradiation.