Su et al recently reported that there was a borderline significantly increased risk of cancer among patients who received amiodarone compared with the general population. This interesting study appears to be the first large, population-based, cohort study to evaluate the risk of cancer among patients treated with amiodarone. Patients of either male sex or those treated with > 180 cumulative defined daily doses within the first year were found to have a significantly higher risk of developing cancer, and those with both factors had an even greater standardized incidence ratio of 1.46 (P = .008).
Amiodarone has many adverse effects and toxicities occur in multiple organ systems, especially the lung, skin, liver, and thyroid gland. In postmarketing surveillance, the US Food and Drug Administration reported the development of lung masses, thyroid cancer, and skin cancer after treatment with amiodarone. To our knowledge, to date there is no proven relation between amiodarone and cancer; in addition, Su et al did not demonstrate this finding.
It is well known that the average American diet contains approximately 150 μg/day of iodine, but amiodarone contains 75 mg of iodine per tablet and has a half-life of months. To our knowledge, there have been no data published to date demonstrating that iodine may trigger carcinogenesis in normal tissue, but Guan et al established that high iodine intake appears to be a significant risk factor for the occurrence of BRAF mutations in the thyroid gland and therefore may be a risk factor for the development of papillary thyroid cancer. Many epidemiological studies have suggested that environmental factors may include a high intake of iodine with a regular diet.[3, 4] It is our hypothesis that excess iodine may cause BRAF mutations in healthy subjects because it is well established that acquired mutations in this gene have been found in cancers, including non-Hodgkin lymphoma, colorectal cancer, malignant melanoma, papillary thyroid carcinoma, non-small cell lung carcinoma, and adenocarcinoma of the lung. Additional studies are needed to establish this relationship between BRAF mutations and excess iodine.