Amiodarone may increase cancer risk

Amiodarone has been associated with increased risk for cancer, especially in men and those exposed to high amounts of the arrhythmia drug, according to study results in Cancer.

The population-based cohort study included 6,418 patients treated with amiodarone between 1997 and 2008.

During a median follow-up of 2.5 years, 280 patients developed cancer. Risk for cancer increased with borderline significance (SIR=1.12; 95% CI, 0.99-1.26; P=.067) compared with the general population, according to the study abstract.

Men were at greater risk for developing cancer (SIR=1.18; 95% CI, 1.02-1.36) compared with women (SIR=0.99; 95% CI, 0.79-1.23).

“One possible explanation for this difference is that there is a 37% higher clearance rate of amiodarone in females than in males because of differences in cytochrome P450 3A4 activity and the percentage of body fat,” the researchers wrote.

Researchers found an increased risk for cancer within 1 year of amiodarone use (SIR=1.32; 95% CI, 1.05-1.64), but not after 1 year (SIR=1.02; 95% CI, 0.89-1.18). However, there was an increased risk for cancer after 3 years in patients with more than 180 cumulative defined daily doses of amiodarone among the total cohort (SIR=1.28; 95% CI, 1.00-1.61) and in men (SIR=1.46; 95% CI, 1.11-1.89). Those with less than 180 cumulative defined daily doses of amiodarone were not at higher risk for developing cancer.

Previous research and postmarketing surveillance by the FDA has reported a possible association between amiodarone therapy and development of lung masses, thyroid cancer and skin cancer, according to background information.

In this study, the researchers found no significant differences in the incidence of specific cancer types, including lung and mediastinum, thyroid cancer, or skin cancer, when compared with the general population.

“To the best of our knowledge, the current study is the first large, population-based, cohort study to evaluate the risk of cancer among patients treated with amiodarone,” the researchers wrote.

“Although extensive screenings for occult cancers in patients currently undergoing treatment with amiodarone appears to be impractical, we suggest that cancer events should be routinely reported in future amiodarone trials, and further observational research is necessary.”

This study included patients in the Taiwan National Health Insurance Research database. About 43% were women and median age at diagnosis was 70 years.

For more information:

Su VY. Cancer. 2013;doi:10.1001/cncr.27881.

Disclosure: The researchers report no relevant financial disclosures.