TOR is reported to be as effective, or more effective, than TAM on both DFS and OS for postoperative adjuvant therapy. The incidence rate and severity of its adverse effects are similar to those of TAM as shown in two clinical trials, the Finnish Breast Cancer Group (FBCG) and the International Breast Cancer Study Group (IBCSG). Although no significant difference was observed in these trials, other studies report that TOR produced a lower number of thromboembolism events compared with TAM, a undesirable side effect seen in patients treated with TAM. Additionally, compared with TAM, TOR showed less endometrial hypertrophy which is induced by estrogen.