In the Journals

Hyperthyroidism treatment modality does not affect cancer risk

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August 12, 2015

The overall risk for cancer was not increased among patients with hyperthyroidism treated with thyroidectomy or radioactive iodine therapy, according to recent study findings published in The Journal of Clinical Endocrinology & Metabolism.

Essi Ryödi, MD, of Tampere University Hospital in Finland, and colleagues evaluated data from the Hospital Discharge Registry (1986-2007) on 4,334 patients treated surgically for hyperthyroidism and 1,814 treated with radioactive iodine (RAI) therapy at Tampere University Hospital to determine the effect of treatment on cancer morbidity and mortality. Three age- and sex-matched controls also were evaluated for each patient. Follow-up began 3 months after treatment and ended at cancer diagnosis, death, emigration or Dec. 31, 2009.

Before follow-up, 7.3% of patients with hyperthyroidism had cancer vs. 4.7% of controls. During follow-up, new cancers were diagnosed in 10.2% of patients with hyperthyroidism and 10.4% of controls; this revealed no significant difference in cancer incidence between the two groups (RR = 1.05; 95% CI, 0.96-1.15). However, compared with controls, patients with hyperthyroidism had increased risks for respiratory tract cancers (RR = 1.46; 95% CI, 1.05-2.02) and stomach cancer (RR = 1.64; 95% CI, 1.01-2.68).

The risk for cancer was predicted by male sex (HR = 1.74; 95% CI, 1.49-2.03) and increasing age (HR = 1.08/year; 95% CI, 1.08-1.09) but not by treated hyperthyroidism (HR = 1.11; 95% CI, 0.96-1.28).

Treatment type was not associated with the risk for cancer (HR = 1.03; 95% CI, 0.86-1.23), and cancer mortality did not differ between the two groups (HR = 1.04; 95% CI, 0.9-1.2).

“In conclusion, there seems to be an increased risk of gastric and respiratory tract cancers in patients with hyperthyroidism, but the treatment modality (RAI vs. thyroidectomy) does not have an influence on cancer incidence, according to this long-term follow-up study,” the researchers wrote. – by Amber Cox

Disclosure: The researchers report no relevant financial disclosures.