Radiation and Host Factors in Human Thyroid Tumors Following Thymus Irradiation

Abstract

NOMENCLATURE RR relative risk O/E observed to expected ratio z rate/ lo6 PY-rad standard deviate on the normal distribution excess tumors/106 personslyrlrad PY person-years at riskAbstract-In this paper thyroid tumor data from the 1971 survey of the Rochester, New York thymus irradiated population are further analyzed to study radiobiological and host factors. The analyses were based on the approx. 2650 irradiated subjects and 4800 sibling controls who had 5 or more years of follow-up. Twenty-four thyroid cancers and 52 thyroid adenomas were found in the irradiated group, and 0 thyroid cancers and 6 adenomas among the controls. The overall risk estimates were 3.8 thyroid cancers/ lo6 PY-rad and 4.5 thyroid adenomas/106 PY-rad. The dose-response data (thyroid dose range of 5 to > 1000rad) for thyroid cancer indicate both a linear and a dose-squared component, but no dose-squared component is evident for thyroid adenomas. At lower total doses ( <400 rad) there was a suggestion that dose fractionation diminished the thyroid cancer response, but a similar fractionation effect was not found for thyroid adenomas. The temporal pattern of tumors suggested an extended plateau of excess tumor production, rather than a "wavelike" temporal pattern. There was no evidence for an inverse relationship between thyroid radiation dose and thyroid cancer latency. Female and Jewish subjects had a higher risk of radiation-induced thyroid cancer than did their respective counterparts. The additive and multiplicative models of radiation effects were compared with respect to sex differences; neither model provided a superior fit to the data. The tentative nature of the conclusions is stressed because of the relatively small number of thyroid cancers.

Radiation Carcinogenesis in Dogs Irradiated During Prenatal and Postnatal Development

“…While, from this, the dog might appear to have a generally high sensitivity to radiation carcinogenesis, there is little question that this trend is most pronounced in dogs irradiated in the perinatal period, considering both the heightened responses in the young dogs and the greater degree of response throughout the life-span. The occurrence of thyroid neoplasia in our study, while not related to perinatal exposure, is consistent with the findings in humans which indicate that susceptibility to radiation induced thyroid cancer is greatest in early childhood (Shore et al (1985) )28)). In the dog, as in humans, both benign and malignant thyroid neoplasms resulted after radiation exposure.…”

Increasing thyroid cancer incidence in Canada, 1970–1996: time trends and age-period-cohort effects

“…Ionizing radiation is a main well-established risk factor for thyroid cancer (Shore et al, 1985;Franceschi and Vecchia, 1994;Ron, 1995). For the general population, diagnostic radiology may be the main source of exposure to ionizing radiation, and an increased risk associated with diagnostic X-rays is also biologically plausible (Shore et al, 1985;Franceschi and Vecchia, 1994).…”

“…For the general population, diagnostic radiology may be the main source of exposure to ionizing radiation, and an increased risk associated with diagnostic X-rays is also biologically plausible (Shore et al, 1985;Franceschi and Vecchia, 1994). Furthermore, the thyroid gland may be included in the radiation field when either the upper body or the chest is exposed to X-rays.…”

Thyroid Cancer after Chernobyl: Obfuscated Truth

“…The decrease of risk at higher doses is explained by the effect of cell killing (UNSCEAR 2006;Boice 2005). However, no leveling of TC risk was found by Shore et al (1985) at the doses of external radiation up to 10 Gy. In a case-control study following radiotherapy for childhood cancer, it was found that exposures around 60 Gy were associated with a high risk of TC (UNSCEAR 1994).…”