Neoplasia in children treated with X-rays in infancy for thymic enlargement.

Abstract

Irradiation of enlarged thymus glands in infancy, a practice started by Friedlander in 1907 (1), was commonplace in this country from 1930 to 1945. Since many parents and physicians still firmly believe that thymic enlargement is a potentially dangerous condition, x-ray treatments continue to be given to young children with this diagnosis. Because of our interest in possible late sequelae of such x-ray therapy, we have undertaken a survey to determine the present health of 1,722 children treated between 1926 and 1951. Data on the 1,400 children traced to date show that the incidence of malignant neoplasia is high, acute leukemia and thyroid carcinoma being the most common forms of the disease. The high cancer rate in the treated groups is significantly above that in 1,795 untreated siblings and in the general population of the same age distribution. Although the medical literature contains numerous warnings about the possible dangers of the widespread and indiscriminate use of x-rays in the treatment of enlargement of the thymus gland, no concrete substantiating evidence has been presented. Duffy and Fitzgerald (2) suggested a possible association between thyroid cancer in childhood or adolescence and prior irradiation to the thymus gland. In 10 of their series of 28 cases of carcinoma of the thyroid there was a history of x-ray treatment. Two subsequent papers reviewing other series of childhood cancers of the thyroid do not report a history of irradiation (3, 4). Recently Dameshek (5) commented that in one month he had seen 3 children with leukemia who had received roentgen therapy to enlarged thymus glands. Previous attempts to follow children who had received x-ray therapy for thymic enlargement are limited in number and scope. In 1936, Polk and Rose (6) reported a study on 31 of 55 children treated before 1924. Only 18 of the children were less than eighteen months old when treated. One child died of leukemia, but this was only two weeks after treatment. In 1938, Kerley (7) noted that 27 patients were mentally and physically normal twenty-six weeks to sixteen years after irradiation. Conti and Patton (8) reported on a series of 7,400 consecutive newborn infants seen between 1937 and 1946. In the early part of their study, the 3 to 4 per cent of infants found to have roentgen evidence of thymic enlargement were given x-ray therapy whether or not they had symptoms. Later all infants received small doses of x-rays. As this appeared to increase the incidence of respiratory disease, prophylactic roentgen treatments were discontinued. These authors did not observe any cases of neoplasia in their follow-up study, which, however, included only one third of the cases and lasted only a few years for each child. Material Our 1,722 treated cases were taken from the records of three hospitals and from one pediatric and two radiological practices. The majority came from western New York and the rest from the State of Washington.