Abstract: Background and purpose: Tamoxifen is the standard adjuvant endocrine therapy for early premenopausal hormone receptor-positive breast cancer and an important choice for postmenopausal patients. At present, the relationship between tamoxifen treatment and subsequent cataract occurrence is controversial. Methods: The relevant cases from the prospectively maintained database of the Department of Breast Surgery in Shanghai Cancer Center were analyzed. Among 3034 patients, 806 patients did not receive endocrine therapy, 1065 patients were treated with tamoxifen, and 1 163 patients received aromatase inhibitor alone. For patients without tamoxifen treatment and those without endocrine therapy, association study was performed according to the age (≤40 years, 41-50 years, >50 years) and tamoxifen treatment time. Results: Although there was no significant difference in the incidence of cataract between the non-endocrine group (806 patients) and the tamoxifen-treated group (1 065 patients) (HR=1.1, 95% CI: 0.8-1.5; P=0.70), subgroup analyses according to the age showed different outcomes. In the ≤40 years and 40-50 years groups, tamoxifen was not significantly associated with cataract incidence. However, in the >50 years group, tamoxifen treatment led to a significantly higher risk of developing cataract with 1.8 times that of the unused group (15.4 % vs 9.0%, 95% CI: 1.1-3.1; P=0.024). Moreover, multivariate analysis revealed that patients with long-term use of tamoxifen (more than 5 years) also had a higher risk of cataract than those with less than 5-year treatment of tamoxifen. Conclusion: Although the incidence of cataract was not significantly associated with tamoxifen use in the overall population, the risk of cataract was significantly increased in postmenopausal patients and those with long-term tamoxifen medication. When we select tamoxifen candidates, we should pay attention to the assessment of toxicity risk as well as cataract.

Key words: Breast cancer, Tamoxifen, Endocrine therapy, Cataract, Extended therapy