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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.
Ron et al. (Fri,) studied this question.