Risk of cancer among offspring of childhood-cancer survivors. Association of the Nordic Cancer Registries and the Nordic Society of Paediatric Haematology and Oncology.

Increasing numbers of children with cancer survive and reach reproductive age. However, the risk of cancer (other than retinoblastoma) in the offspring of survivors of childhood and adolescent cancer is uncertain. Using data from national cancer and birth registries, we assessed the risk of cancer among 5847 offspring of 14,652 survivors of cancer in childhood or adolescence diagnosed since the 1940s and 1950s in Denmark, Finland, Iceland, Norway, and Sweden. The offspring were followed up for a diagnosis of cancer for 86,780 person-years, and standardized incidence ratios were calculated. Among the 5847 offspring, 44 malignant neoplasms were diagnosed (standardized incidence ratio, 2.6; 95 percent confidence interval, 1.9 to 3.5). There were 17 retinoblastomas, yielding a standardized incidence ratio of 37. There were 27 neoplasms other than retinoblastoma (standardized incidence ratio, 1.6; 95 percent confidence interval, 1.1 to 2.4). The second most common primary site of cancer among the offspring was the brain and nervous system, in which eight tumors were observed (standardized incidence ratio, 2.0; 95 percent confidence interval, 0.9 to 3.9.) There were between zero and four apparently sporadic cases of cancer in other primary sites among the offspring. Excluding 4 likely cases of hereditary cancer and 2 subsequent cancers among the offspring with hereditary retinoblastoma, there were 22 sporadic cancers, for a standardized incidence ratio of 1.3 (95 percent confidence interval, 0.8 to 2.0). There is no evidence of a significantly increased risk of nonhereditary cancer among the offspring of survivors of cancer in childhood.