Tamoxifen is an effective endocrine treatment for early
breast cancer (EBC) but increases the risk of
venous thromboembolism. Whether Asian EBC patients (pts) bear the same risk when treated with adjuvant
tamoxifen is uncertain. EBC pts diagnosed between 2004 and 2009 were selected from a population database in Taiwan. The pts were followed up from the index date to December 31, 2011 to collect events of
deep vein thrombosis (DVT) and
pulmonary embolism (PE). Cumulative incidence rates and hazard ratios (HRs) were used to compare the risk between pts treated with and without
tamoxifen. In addition, comorbidities were included in an adjusted model of the risk of DVT and PE. A total of 28,029 EBC pts, including 17,843 (63.8 %) in the
tamoxifen group and 10,155 (36.2 %) in the nontamoxifen group, were analyzed. The 7-year cumulative incidence rates for DVT and PE were 2.58 and 0.32 % in the
tamoxifen group and 2.51 and 0.32 % in the nontamoxifen group (P = 0.92 for DVT, P = 0. 65 for PE), respectively. The HR for the nonadjusted and adjusted models showed no differences in DVT and PE risks between the
tamoxifen and nontamoxifen groups. The
uterine cancer risk was significantly increased in the pts receiving
tamoxifen (adjusted HR = 2.79, P < 0.001), suggesting
tamoxifen compliance. The risks of developing DVT and PE are not increased in Asian EBC pts receiving adjuvant
tamoxifen. Ethnicity differences should be considered when discussing optimal endocrine treatments with EBC pts.