Radiobiology

Radiobiology > In Utero Exposure > Carcinogenesis

Carcinogenesis Risk

Carcinogenesis and in utero irradiation

While cancer is the leading cause of death in U.S. children outside of the neonatal period and until 15 years of age, it is important to note that malignancy is rare in this age group.

According to SEER statistics considering all children regardless of exposures, a male infant has a 1 in 300 (0.3%) chance of developing cancer before age 20 years old; a female has slightly less risk, about 1 in 333. Risk of dying from cancer is much lower (in the U.S., about 2,500 children died of cancer in 1998).
Genes associated with increased cancer risk number about 143, and about half are dominant. Ionizing radiations may induce somatic expression of such oncogenes.
Reports suggest that increased cancer risk is directly proportional to the number of maternal radiographs received during pregnancy. The data of Stewart and others indicate a linear relationship between cancer frequency in the first 10 years of life and radiation dose during intrauterine life.
When considering cancer types, leukemia is the greatest risk – incidence peaks at 4-5 years of life (lymphocytic types present earlier, at an average of 4 years, and myeloid types present at 5 to 9 years).

Epidemiological studies suggest the excess cancer risk to be one in 1,000 or one in 10,000 per rad (1,000 to 10,000 per 10 mGy) for the first 10 years of life. However, studies of children exposed in utero during the atomic bombings of Japan failed to show an increased incidence of childhood cancer.