Association between ¹³¹I treatment for thyroid cancer and risk of receiving cataract surgery: A cohort study from Taiwan

The risk of cataracts after ¹³¹I therapy for cancer is unknown. The objective of this study was to evaluate the association between ¹³¹I therapy for thyroid cancer and risk of receiving cataract surgery in Taiwan. Methods: This was a nationwide populationbased 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 ¹³¹I activity in each patient was calculated. Hazard ratios were calculated using a time-dependent survival analysis to estimate the effect of ¹³¹I 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 ¹³¹I 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 ¹³¹I 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 ¹³¹I activity and age or between ¹³¹I activity and sex was noted (all P > 0.05). Conclusion: ¹³¹I 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.