Neoplasms in Children Treated With X Rays for Thymic Enlargement. I. Neoplasms and Mortality

Demographic information and radiation factors are presented for 2,809 children treated with X rays for thymic enlargement in an upstate New York county between 1926 and 1957. Approximately half the children had been studied previously. The remainder were new cases. Information regarding the health and mortality of the treated children of both series was collected by mail survey in 1959–60. Procedures for tracing families and other methodological aspects of the survey, including the design of the questionnaire and response rates, are described. Radiation dosage factors used in treatment are believed to be accurate. Almost all the children were irradiated before the age of 6 months. Many of the older children were given relatively high doses of X rays to large areas that often involved the posterior as well as the anterior aspects of the chest. The younger children were usually given lower doses of X rays to relatively small anterior areas. The 1,451 children previously studied had a high incidence of tumors, particularly leukemia and thyroid neoplasms. The present survey shows that these children continued to develop tumors at a higher rate than that of their untreated siblings and higher than that expected in a comparable group from the general population. Thyroid adenomas and carcinomas comprise about one half, and osteochondromas, about one sixth of all tumors. No new cases of leukemia have occurred since the previous survey. Several cases of salivary gland tumors and neurilemmomas, which are very rare neoplasms in children and young adults, were observed. Data on mortality of treated children and their siblings in both series are difficult to evaluate. The moderate excess of deaths in the children of series I after the 1st year of life can be attributed largely to 6 cases of leukemia. Relatively few other deaths have resulted from malignant disease.