Thyroid cancer after diagnostic doses of iodine-131: a retrospective cohort study
The incidence of thyroid cancer was evaluated in 35,074 patients examined for suspected thyroid disorders between 1951 and 1969 with an average of 1.92 megabecquerel ((MBq) 52 microCi) of 131I. The radiation dose to the thyroid gland was, on the average, approximately 0.5 Gy. The mean age at the time of examination was 44 years; 5% were under age 20. Patients were followed for an average of 20 years. Record linkage with the Swedish Cancer Register identified 50 thyroid cancers occurring 5 years or more after the initial 131I examination, in contrast to 39.4 expected based on general population rates (standardized incidence ratio (SIR) = 1.27, 95% confidence interval = 0.94-1.67). Risk was highest among males (SIR = 2.70, n = 10), patients followed 5-9 years (SIR = 2.22, n = 23), and patients receiving more than 74 microCi or 2.74 MBq of 131I (SIR = 2.04, n = 17). However, these observations were confounded by the fact that patients examined for a suspected thyroid tumor received the highest 131I exposures and were at highest overall risk (SIR = 2.77, n = 34). Patients given 131I for reasons other than a suspected tumor were not at increased risk (SIR = 0.62, n = 16). Patients anticipated to be at highest risk, i.e., women (SIR = 1.12, n = 40) and those observed for 10 years or more (SIR = 0.93, n = 27), showed no evidence of a dose response. Overall, these data provide little proof that 131I is carcinogenic in humans and support the notion that the carcinogenic potential of internal 131I beta particles might be as low as four times less than external x rays or gamma rays.
- Research Organization:
- Karolinska Hospital, Stockholm (Sweden)
- OSTI ID:
- 6755501
- Journal Information:
- JNCI, J. Natl. Cancer Inst.; (United States), Vol. 80:14
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
IODINE 131
CARCINOGENESIS
NEOPLASMS
RADIOINDUCTION
RADIOTHERAPY
SIDE EFFECTS
THYROID
DOSE-RESPONSE RELATIONSHIPS
PATIENTS
RADIATION DOSES
SEX DEPENDENCE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BODY
DAYS LIVING RADIOISOTOPES
DISEASES
DOSES
ENDOCRINE GLANDS
GLANDS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
ISOTOPES
MEDICINE
NUCLEAR MEDICINE
NUCLEI
ODD-EVEN NUCLEI
ORGANS
PATHOGENESIS
RADIOISOTOPES
RADIOLOGY
THERAPY
560151* - Radiation Effects on Animals- Man