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Radioactive iodine for thyroid cancer may not increase breast cancer risk
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The risk for or recurrence of breast cancer may not be increased for patients with thyroid cancer undergoing radioactive iodine treatment, according to recent study findings published in The Journal of Clinical Endocrinology & Metabolism.
“Despite a number of studies that suggested a link between [radioactive iodine] treatment and breast cancer, a recent meta-analysis of multicenter studies showed that the risk of a second primary breast cancer was not related to the use of [radioactive iodine],” the researchers wrote. “These contrasting results suggests that the relationship between [radioactive iodine] therapy and the development of breast cancer among thyroid cancer patients needs to be further evaluated.”
Young Joo Park, MD, PhD, of Seoul National University in Korea, and colleagues evaluated data from 6,150 women with thyroid cancer diagnosed between 1973 and 2009 at Seoul National University Hospital to determine the effect of radioactive iodine (RAI) treatment on the development and recurrence of breast cancer among these patients. Follow-up occurred until December 2012 and revealed 99 cases of breast cancer. Overall, 59% were undergoing RAI therapy.
Among the whole cohort, the proportion of papillary thyroid cancer, a larger thyroid tumor, extrathyroidal invasion, an advanced T stage or lymph node metastasis was higher among the RAI group compared with the group not on RAI (P < .01 for each comparison).
Researchers also evaluated a 2-year latency cohort (n = 6,080) whose breast cancer was diagnosed at least 2 years after the thyroid cancer diagnosis (n = 28); the cohort was divided into two groups, those on RAI (59.1%) and those not (41.9%).
Researchers found that among this cohort, the RAI group did not have a significantly higher risk for breast cancer compared with the no RAI group (HR = 0.49; 95% CI, 0.22-1.06). However, high-dose RAI ( 120 mCi) reduced the risk for incident breast cancer (HR = 0.17; 95% CI, 0.05-0.62).
Among patients aged younger than 30 years, the risk for breast cancer was not higher in the RAI group (HR = 1.52; 95% CI, 0.1-22.74) or the group taking higher doses (HR = 1.82; 95% CI, 0.08-44.14).
“In summary, there was no increase in the occurrence or recurrence of breast cancer in patients with primary thyroid cancer who had undergone RAI treatment,” the researchers wrote. “These results indicate that RAI treatment can be used without increasing the risk of breast cancer.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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