High dose toremifene in advanced breast cancer resistant to or relapsed during tamoxifen treatment

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Abstract
Fifty patients with advanced breast cancer refractory to prior tamoxifen therapy were assigned to investigational treatment with high-dose toremifene administered 120 mg orally twice a day. Treatment was generally well tolerated. The majority (80%) of the patients had no side effects, and among the remaining 10 patients reported side effects were mostly mild and/or transient. Two objective tumor responses were observed: one complete response (CR), duration 6.2 months, and one partial response (PR), duration 8 months. The response rate was thus 4% (95% CI: 0.5 to 14%). In addition 3 patients experienced a mixed response, some metastatic sites responding, while at other sites disease progressed; 22 patients had disease stabilization for > 2 months. A subset analysis disclosed that a small subgroup of patients, including 7 patients in this study, who had achieved CR at some of the sites during preceding tamoxifen therapy, experienced a long progressionfree time during high dose toremifene treatment. The median time to progression in this subgroup of patients was 9.4 months (95% CI: 3.8 to 9.4) as opposed to 2.1 months (95% CI: 2.0 to 2.8) for all the remaining 43 patients, which is a significant decrease in disease progression (p < 0.03). Such results reveal that although this kind of second-line hormonal treatment with high dose toremifene cannot be recommended for all tamoxifen failures, there might be a subset of patients, i.e. those who achieve CR in some lesion during tamoxifen therapy, who benefit from this type of treatment.