Randomized double-blind phase 2 trial of 3 doses of TAS-108 in patients with advanced or metastatic postmenopausal breast cancer

Cancer, 04/24/2012

Buzdar A et al. – TAS–108 at 40mg and 80mg daily demonstrated clinical activity with an encouraging duration of benefit. Because of its superior safety profile, TAS–108 40mg daily is recommended for further development.


  • In this randomized, double-blind, multicenter study, TAS-108 was administered daily at a dose of 40mg, 80mg, or 120mg to postmenopausal patients with locally advanced, or inoperable, or metastatic hormone-receptor positive breast cancer.
  • The primary efficacy outcome was clinical benefit (CB), defined as the total number of patients who achieved a complete response, a partial response, or stable disease for ≥24weeks.
  • The study was a 2-stage design in which 19 patients per dose group were planned in the first stage.
  • If at least 3 patients in any dose group achieved a CB, then that dose group was to be allowed to continue enrolling for the second stage, and the group could include up to a total of 60 patients.


  • The 40-mg and 80-mg groups met the criterion and enrolled patients into the second stage.
  • In the 40-mg group, there were 13 CB events in 60 patients (21.7%); and, in the 80-mg group, there were 12 CB events in 60 patients (20%).
  • The 120-mg daily dose was stopped early, because it failed to achieve the criterion.
  • For the 40-mg and 80-mg groups, the median time to progression was 15.0weeks and 15.9weeks, respectively.
  • Only 1 drug-related serious adverse event (grade 3 hyperglycemia) was reported.

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