Thyroid Cancer among Persons Given X-ray Treatment in Infancy for an Enlarged Thymus Gland
Level 3 - non-randomized controlled study
Non-randomized controlled cohort study with sibling controls
OpenAlex W2136591540 · doi:10.1093/oxfordjournals.aje.a116610
What was done
A cohort of 2,657 infants in Rochester, New York, who received x-ray radiation treatment for an enlarged thymus gland, along with 4,833 unexposed sibling controls, was tracked via mail surveys through about 1986 (mean follow-up: 37 years). Estimated thyroid radiation doses ranged from 0.03 to >10 Gy (62% received >0.5 Gy). The study evaluated pathologically diagnosed thyroid cancer incidence, dose-response relationships, and interactions with other potential risk factors.
What was found
There were 37 pathologically confirmed thyroid cancers in the irradiated group versus 5 in sibling controls. The dose-response relationship was linear, with an estimated relative risk at 1 Gy of 10 (90% confidence interval: 5–23). Thyroid cancer rates were significantly elevated even at low doses (0–0.3 Gy; significant positive slope). Excess relative risk declined over time but remained elevated for at least 45 years after exposure. Older age at first childbirth was associated with thyroid cancer risk, and radiation interactions suggested higher radiogenic risk among Jewish subjects and women with older age at menarche or first childbirth.
Why it matters
This study provides long-term epidemiological evidence that childhood ionizing radiation exposure causes a substantial, linear, dose-dependent increase in thyroid cancer risk persisting decades into adulthood.
Limits
Follow-up was conducted primarily through mail surveys, creating potential for non-response and reporting biases. Radiation doses were retrospectively estimated rather than directly measured. The cohort reflects a specific historical medical practice in a single geographic area.
Cited by
- supports Between the 1910s and 1940s, infants routinely underwent thymus irradiation to prevent sudden infant death syndrome (status thymicolymphaticus), causing thousands of subsequent cancer deaths.