PURPOSE: The principal objectives of this study were to estimate the incidence of second tumors among children treated for heritable retinoblastoma during a 50-year period and to investigate the relationship between these tumors and previous radiation therapy. METHODS: The records of all retinoblastoma patients examined at the Mayo Clinic from 1941 through 1990 were retrospectively reviewed. The therapeutic modality used to manage the tumor, the occurrence of any second malignancy, and current follow-up on all patients were evaluated. RESULTS: Eighty-two (46%) of 180 children with retinoblastoma had bilateral tumors (76 patients) or unilateral disease and a positive family history (six patients) and were followed for an average of 21.8 years (range, 1 month to 53 years). The Kaplan-Meier estimates of second nonocular tumors among the 82 patients with heritable retinoblastoma were 12% at 10 years, 16% at 25 years, and 30% at 40 years. Although 14 of the 15 patients who developed second malignancies had received radiation therapy, only four of the malignancies occurred within the field of irradiation. CONCLUSIONS: The relatively low incidence of second tumors among long-term survivors of heritable retinoblastoma in this series of patients occurred predominantly outside the field of irradiation. The variable incidence of second nonocular malignancies in previous reports may reflect variations in radiation technique and dosage.
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