Phase III randomized adjuvant study of tamoxifen alone versus sequential tamoxifen and anastrozole in Japanese postmenopausal women with hormone-responsive breast cancer: N-SAS BC03 study

Tomohiko Aihara, Yuichi Takatsuka, Shozo Ohsumi, Kenjiro Aogi, Yasuo Hozumi, Shigeru Imoto, Hirofumi Mukai, Hiroji Iwata, Toru Watanabe, Chikako Shimizu, Kazuhiko Nakagami, Motoshi Tamura, Toshikazu Ito, Norikazu Masuda, Nobuo Ogino, Kazufumi Hisamatsu, Shoshu Mitsuyama, Hajime Abe, Shiro Tanaka, Takuhiro YamaguchiYasuo Ohashi

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)

Abstract

Clinical trials conducted in Western countries have shown that aromatase inhibitors are associated with better disease-free survival (DFS) than tamoxifen in postmenopausal early breast cancer. Because pharmacogenetic differences in drug-metabolizing genes may cause ethnic differences, assessment of the efficacy and tolerability of aromatase inhibitors in non-white women is warranted. This open-label, randomized clinical trial included 706 postmenopausal Japanese women with hormone-receptorpositive breast cancer, who had received tamoxifen for 1 to 4 years as adjuvant therapy. This study was closed early after entry of ∼28% of the initially planned patients. They were randomly assigned to either switch to anastrozole or to continue tamoxifen for total treatment duration of 5 years. Primary endpoints were DFS and adverse events. At a median follow-up of 42 months, the unadjusted hazard ratio was 0.69 (95% confidence interval, 0.42-1.14; P = 0.14) for DFS and 0.54 (95% CI, 0.29-1.02; P = 0.06) for relapse-free survival (RFS), both in favor of anastrozole. The incidence of thromboembolic events in the tamoxifen group and bone fractures in the anastrozole group was not excessively high. Switching from tamoxifen to anastrozole was likely to decrease disease recurrence in postmenopausal Japanese breast cancer patients. Ethnic differences in major adverse events may be attributable to a low baseline risk of these events in Japanese.

Original languageEnglish
Pages (from-to)379-387
Number of pages9
JournalBreast Cancer Research and Treatment
Volume121
Issue number2
DOIs
Publication statusPublished - 2010 Jun
Externally publishedYes

Keywords

  • Adjuvant therapy
  • Anastrozole
  • Breast cancer
  • Ethnic difference
  • Hormonal therapy
  • Tamoxifen

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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