The mortality experience of 10,834 children treated with x-rays for
ringworm of the scalp between 1948 and 1960, 10,834 matched comparison subjects, and 5,392 siblings was evaluated over an average follow-up period of 26 years. Mortality was ascertained by linking unique personal identification numbers of study subjects with the national death registry.
Radiotherapy in childhood was associated with an increased risk of death due to
tumors of the head and neck (relative risk (RR) = 3) and
leukemia (RR = 2.3). No other causes of death were significantly elevated after irradiation. The excess of
brain tumors (average intracranial dose = 150 rads) confirms that the central nervous system of the child is sensitive to the induction of
cancers by radiation. The bone marrow dose averaged over the entire body was approximately 30 rad, and the estimated risk coefficient of 0.9 excess
leukemias per million per year per rad is consistent with other studies of whole-body exposure. A significant excess of bone and
soft tissue sarcomas (RR = 9) was also observed. The pattern of
cancer risk over time was bimodal; an early peak due to excess
leukemias occurred within a few years of exposure, whereas excesses of solid
tumors were most apparent after about 15 years. Despite the excess of
cancers among exposed persons, over 50% of the deaths in the entire study population were from external events, mainly accidents or events related to military service. An estimate of the total impact of radiogenic
cancer after childhood irradiation will require additional years of observation since the population irradiated is just now entering the age ranges normally associated with high
cancer risk.