Breast Cancer Research and Treatment

, Volume 121, Issue 2, pp 379–387

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


    • Breast Center, Aihara Hospital
  • Yuichi Takatsuka
    • Department of Breast SurgeryKansai Rosai Hospital
  • Shozo Ohsumi
    • Department of Breast OncologyNational Hospital Organization Shikoku Cancer Center
  • Kenjiro Aogi
    • Department of Breast OncologyNational Hospital Organization Shikoku Cancer Center
  • Yasuo Hozumi
    • Department of Breast and General SurgeryJichi Medical University
  • Shigeru Imoto
    • Department of Breast Surgery, School of MedicineKyorin University
  • Hirofumi Mukai
    • Division of Oncology and HematologyNational Cancer Center Hospital East
  • Hiroji Iwata
    • Department of Breast OncologyAichi Cancer Center Hospital
  • Toru Watanabe
    • Department of Medical OncologyHamamatsu Oncology Center
  • Chikako Shimizu
    • Division of Breast and Medical OncologyNational Cancer Center Hospital
  • Kazuhiko Nakagami
    • Department of Breast SurgeryShizuoka General Hospital
  • Motoshi Tamura
    • Department of SurgeryKKR Sapporo Medical Center
  • Toshikazu Ito
    • Department of SurgeryRinku General Medical Center
  • Norikazu Masuda
    • Department of Surgery, Breast OncologyOsaka National Hospital
  • Nobuo Ogino
    • Department of SurgeryTondabayashi Hospital
  • Kazufumi Hisamatsu
    • Department of SurgeryHiroshima City Asa Hospital
  • Shoshu Mitsuyama
    • Department of SurgeryKitakyushu Municipal Medical Center
  • Hajime Abe
    • Department of SurgeryShiga University of Medical Science
  • Shiro Tanaka
    • Division of Clinical Trial Design & Management, Translational Research CenterKyoto University
  • Takuhiro Yamaguchi
    • Department of Clinical Trial Data Management, Graduate School of MedicineUniversity of Tokyo
  • Yasuo Ohashi
    • Department of Biostatistics, School of Public HealthUniversity of Tokyo
Clinical trial

DOI: 10.1007/s10549-010-0888-x

Cite this article as:
Aihara, T., Takatsuka, Y., Ohsumi, S. et al. Breast Cancer Res Treat (2010) 121: 379. doi:10.1007/s10549-010-0888-x


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-receptor-positive 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.


Adjuvant therapyAnastrozoleBreast cancerEthnic differenceHormonal therapyTamoxifen

Copyright information

© Springer Science+Business Media, LLC. 2010