NSABP B 23

• Several preclinical studies have demonstrated that tamoxifen acts not only by blocking the ER pathway, but also by:
  • Modulating the production of transforming growth factor-alpha and transforming growth factor-beta
  • By increasing the levels of sex hormone-binding globulin in serum
  • By increasing natural killer cell counts
  • By decreasing insulin-like growth factor

• The NSABP protocol B-23:
  • Was developed to determine whether tamoxifen has a role in patients with ER negative cancer
  • Patients with ER negative tumors were randomized to:
    • Four cycles of adjuvant doxorubicin and cyclophosphamide (AC) or 6 cycles of adjuvant cyclophosphamide, methotrexate, and fluorouracil (CMF) with or without tamoxifen
  • The results of B-23 demonstrated:
    • No significant improvement in DFS or overall survival (OS) with tamoxifen added to chemotherapy:
      • DFS: CMF, 83%; CMF plus tamoxifen, 83%; AC, 83%; AC plus tamoxifen, 82%
      • OS: CMF, 89%; CMF plus tamoxifen, 89%; AC, 90%; AC plus tamoxifen, 91%
    • Additionally, protocol B-23 confirmed the results of protocol B-15:
      • That found that four cycles of AC are equivalent to 6 cycles of CMF in terms of DFS and OS
• NSABP B-24 also demonstrated the effectiveness of tamoxifen only on ER positive ductal carcinoma in situ (DCIS), as did a study by Allred et al. on the risk reduction of a subsequent breast cancer in ER positive DCIS treated with tamoxifen
• References:
  • Fisher B, Anderson S, Tan-Chiu E, Wolmark N, Wickerham DL, Fisher ER,et al. Tamoxifen and chemotherapy for axillary node-negative, estrogen receptor-negative breast cancer: findings from National Surgical Adjuvant Breast and Bowel Project B-23. J Clin Oncol. 2001;19(4):931-942.
  • Wapnir IL, Dignam JJ, Fisher B, Mamounas EP, Anderson SJ, Julian TB, et al. Long-term outcomes of invasive ipsilateral breast tumor recurrences after lumpectomy in NSABP B-17 and B-24 randomized clinical trials for DCIS. J Natl Cancer Inst. 2011;103(6):478-488.
  • Allred DC, Anderson SJ, Paik S, Wickerham DL, Nagtegaal ID, Swain SM, et al. Adjuvant tamoxifen reduces subsequent breast cancer in women with estrogen receptor-positive ductal carcinoma in situ: a study based on NSABP protocol B-24. J Clin Oncol. 2012;30(12):1268-1273.

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