ARTICLE

Retinoblastoma is a rare malignant tumor that arises in the retina. Patients with a positive family history of retinoblastoma and those with bilateral retinoblastoma are carriers of a germline mutation of the RB1 gene and are classifi ed as hereditary (30 % – 40%). Unilateral patients without a family history (60 % – 70%) are classifi ed as hav-ing nonhereditary disease, where retinoblastoma is presumably caused by somatic mutations of the RB1 gene ( 1 – 3). Unlike survivors of nonhereditary retinoblastoma, survivors of hereditary retinoblastoma have an elevated risk of developing sec-ond malignancies ( 4, 5). Initial reports suggested that the increased risk of second malignancies could be attributed to irradiation ( 6 – 9), and we showed that patients with hereditary disease treated with radiotherapy are more susceptible to developing second malignan-cies compared with patients with hereditary disease treated other-wise ( 5). Subsequent studies demonstrated that the risk of secon