[Assessment of post-administration body distribution of toremifene and tamoxifen, and their administration regimens].

: Toremifene is an anti-estrogenic drug like tamoxifen. We assessed the body distributions after administration of toremifene and tamoxifen in order to evaluate their treatment regimens by measuring the concentrations in tissues. It is known that, after toremifene (TOR) or tamoxifen (TAM) is consecutively administered to breast cancer patients, TOR or TAM and their main active N-desmethyl-metabolites (TOR-1 or TAM-1) are detected in sera, tumor tissues, and lymph nodes. Accordingly, after we administered toremifene or tamoxifen to primary breast cancer patients previous to surgery, we measured the concentrations of TOR, TOR-1, TAM, TAM-1 in sera, tumor tissues, and lymph nodes. We found that the concentrations of TOR and TOR-1 in sera, tumors, and lymph nodes reached a peak about 2 weeks after administration of toremifene 40 mg. Likewise, the concentrations of TAM and TAM-1 in sera, tumors, and lymph nodes reached a peak about 2 weeks after administration of tamoxifen, although the peak levels were lower than those of TOR or TOR-1. The concentrations of TAM-1 in lymph nodes were significantly and positively correlated to the duration of administration of TAM, and it was predicted that the concentration of TAM-1 in lymph nodes would reach a steady state at more than 4 weeks after administration of tamoxifen. The concentrations of TOR and TOR-1 were higher in tumors and lymph nodes than in sera. Furthermore, the concentrations of TOR and TOR-1 were significantly higher than those of TAM and TAM-1 in sera and tumors, respectively. Moreover, the concentration in tissue increased in a dose-dependent manner with administration of toremifene 120 mg. There were no significant differences between breast cancers positive and negative for estrogen receptors, with regard to the concentrations of TOR and TOR-1 in either sera, tumors, or lymph nodes. In conclusion, it would be expected that treatment with toremifene might be more effective for breast cancer than that with tamoxifen.