Association Between 131I Treatment for Thyroid Cancer and Risk of Receiving Cataract Surgery: A Cohort Study from Taiwan.

UNLABELLED: The risk of cataracts after (131)I therapy for cancer is unknown. The objective of this study was to evaluate the association between (131)I therapy for thyroid cancer and risk of receiving cataract surgery in Taiwan. METHODS: This was a nationwide population-based cohort study of patients with thyroid cancer diagnosed during the period 1998-2008. The data were obtained from the Taiwan National Health Insurance Research dataset. The cumulative (131)I activity in each patient was calculated. Hazard ratios were calculated using a time-dependent survival analysis to estimate the effect of (131)I therapy on the risk of receiving cataract surgery. RESULTS: A total of 8,221 patients were eligible for the final analysis (mean age, 43.2 y; mean follow-up, 5.9 y); 69% received (131)I with a median cumulative activity of 3.7 GBq. Two hundred patients received cataract surgery. The adjusted hazard ratios were 0.77 (95% confidence interval, 0.54-1.09), 0.92 (95% CI, 0.64-1.31), and 1.06 (95% CI, 0.58-1.94) for cumulative (131)I activities of 0.1-3.6, 3.7-7.3, and 7.4 GBq or more, respectively, compared with a cumulative activity of 0. No trend was noted (P = 0.85). No interaction between (131)I activity and age or between (131)I activity and sex was noted (all P > 0.05). CONCLUSION: (131)I treatment for thyroid cancer did not increase the risk of receiving cataract surgery up to 10 y after treatment. However, further research with direct lens examination and a longer follow-up period is needed to assess subtle and late adverse effects beyond 10 y.