Cancer mortality following cardiac catheterization: a preliminary follow-up study on 4,891 irradiated children.

A retrospective cohort study was conducted on the risk of radiation-induced cancer mortality following cardiac catheterization. The study included 4,891 children with congenital heart disease who were assessed by cardiac catheterization during 1946 to 1968 at The Hospital for Sick Children, Toronto. The cohort was matched against the Ontario cancer death file from 1950 to 1975. The average period of follow-up was 13 years and more than 66,000 person-years have been accrued from the cohort. No deaths from breast cancer or thyroid cancer were identified. Five cancer deaths were observed and compared with 4.8 expected deaths based on Ontario cancer death rates. The five cancer deaths resulted from three leukemias, one Wilms' tumor, and one unspecified nervous system tumor. The preliminary findings did not demonstrate a significant leukemia risk arising from diagnostic cardiac catheterizations. Continued follow-up of this cohort is required to evaluate the risk of breast and thyroid cancers which can occur more than 20 years following radiation exposure.