Tamoxifen and cataracts: a null association

Background. Previous studies have reported an increased risk of cataract for breast cancer patients treated with tamoxifen. We assessed whether breast cancer patients treated with tamoxifen were at increased risk of developing cataracts compared to women not prescribed tamoxifen. Methods. We used a nested, matched case-control study design and data collected in the General Practice Research Database. We identified all women 30-79 years old who were diagnosed with breast cancer and treated with tamoxifen within 6 months, or with bladder cancer, colorectal cancer or non-melanoma skin cancer between January 1991 and December 1999. From this population, we identified all newly diagnosed cases of cataract. We matched four female controls to each case on age (+/-1 year), index date and study entry date (+/-6 months). We assessed the risk of cataracts for current, past and ever users of tamoxifen and according to cumulative use of tamoxifen. We calculated adjusted odds ratios (AOR) and 95% confidence intervals (CI) controlling for the matching factors and adjusting for important cataract risk factors. Findings. Current tamoxifen users were at no increased risk of cataract (AOR = 1.0, 95% CI: 0.7, 1.4). There was no evidence of an increased risk with increasing cumulative dose. Interpretation. We detected no increased risk of cataract among breast cancer patients who were treated with tamoxifen compared to women with other cancers who were not prescribed tamoxifen.