HealthDay News — Pooled cancer risk after exposure to radioactive iodine (RAI) therapy for hyperthyroidism is not significantly elevated, according to a review published online September 17 in JAMA Network Open.

Sung Ryul Shim, PhD, from the Korea University College of Medicine in Seoul, and colleagues conducted a systematic literature review and meta-analysis of data from studies examining site-specific cancer incidence and mortality after RAI treatment for hyperthyroidism.

Based on data from 12 studies (479,452 participants), the researchers found that the overall pooled cancer incidence ratio was 1.02 (95% CI, 0.95 to 1.09) and the pooled cancer mortality ratio was 0.98 (95% CI, 0.92 to 1.04) for exposure to RAI therapy vs nonexposure. There were no statistically significant elevations observed in the risk for specific cancers except thyroid cancer incidence (standardized incidence ratio, 1.86; 95% CI, 1.19 to 2.92) and mortality (standardized mortality ratio, 2.22; 95% CI, 1.37 to 3.59). RAI was significantly associated with breast and solid cancer mortality (breast cancer mortality per 370 MBq: 1.35; solid cancer mortality per 370 MBq: 1.14), based on two studies evaluating dose response.

“These findings suggest that radiation-induced cancer risks following RAI therapy for hyperthyroidism are small and, in observational studies, may only be detectable at higher levels of administered dose,” the authors write.

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