The Society for Endocrinology (SfE) and the British Thyroid Association (BTA) have issued a joint statement on the findings of a recent study published in JAMA Internal Medicine, which suggested an increased risk for cancer mortality with radioactive iodine (RAI) therapy.
The study by Kitahara et al reported a statistically positive association of RAI with an increased risk for death from solid cancers in patient with hyperthyroidism, with a relative risk (RR) of solid cancer mortality at 100-mGy dose to the stomach being 1.06 (95% CI, 1.02-1.10; P=.002) and the RR for mortality with female breast cancer was 1.12 (95% CI, 1.003-1.32; P=.04) with 100-mGy dose to the breast. For every 1000 patients receiving typical doses to the stomach (150-250 mGy), Kitahara et al estimated the lifetime excess could be 19-32 solid cancer deaths.
The study has generated considerable concern and debate since it was published in July.
Now, in a statement published in Clinical Endocrinology, the SfE and the BTA have cautioned that the results need to be interpreted with caution because of the modest RRs and several failings in the design of the trial. They point out that a control cohort with hyperthyroidism was not included and say important confounders, such as smoking and obesity, were omitted. Furthermore, they say, the model used to calculate absorbed RAI has not been validated.
“It would be unfortunate if patients were deprived of the option of rapid, effective control of their hyperthyroidism with radioiodine, due to concerns of cancer risk. Overall, on the basis that current evidence shows no excess cancer risk, it would be reasonable to continue with current approaches to the management of hyperthyroidism, whilst further, appropriately controlled studies are undertaken,” the statement says.