Originally published as JCO Early Release 10.1200/JCO.2005.03.0783 on February 27 2006
Journal of Clinical Oncology, Vol 24, No 9 (March 20), 2006: pp. 1332-1341
© 2006 American Society of Clinical Oncology.
Tamoxifen After Adjuvant Chemotherapy for Premenopausal Women With Lymph Node-Positive Breast Cancer: International Breast Cancer Study Group Trial 13-93
International Breast Cancer Study Group
From the International Breast Cancer Study Group. The members and affiliations of the writing committee, as well as the participants and authors of Trial 13-93, are listed in the Appendix
Address reprint requests to Marco Colleoni, MD, Division of Medical Oncology, European Institute of Oncology, Via Ripamonti 435, 20141, Milan, Italy; e-mail: marco.colleoni{at}ieo.it
PURPOSE: The value of adjuvant tamoxifen after chemotherapy for premenopausal women with breast cancer has not been adequately assessed.
PATIENTS AND METHODS: Between 1993 and 1999, International Breast Cancer Study Group Trial 13-93 enrolled 1,246 assessable premenopausal women with axillary node-positive, operable breast cancer. All patients received chemotherapy (cyclophosphamide plus either doxorubicin or epirubicin for four courses followed by immediate or delayed classical cyclophosphamide, methotrexate, and fluorouracil for three courses), which was followed by either tamoxifen (20 mg daily) for 5 years or no further treatment. The primary end point was disease-free survival (DFS). Tumors were classified as estrogen receptor (ER) -positive (n = 735, 59%) if immunohistochemical (IHC) or ligand-binding assays (LBA) were clearly positive. The ER-negative group included all other tumors (n = 511, 41%). A subset of the ER-negative group was defined as ER absent (n = 108, 9%) if IHC staining was none or if the LBA result was 0 fmol/mg cytosol protein. The median follow-up time was 7 years.
RESULTS: Tamoxifen improved DFS in the ER-positive cohort (hazard ratio [HR] for tamoxifen v no tamoxifen = 0.59; 95% CI, 0.46 to 0.75; P < .0001) but not in the ER-negative cohort (HR = 1.02; 95% CI, 0.77 to 1.35; P = .89). Tamoxifen had a detrimental effect on patients with ER-absent tumors compared with no tamoxifen in an unplanned exploratory analysis (HR = 2.10; 95% CI, 1.03 to 4.29; P = .04). Patients with ER-positive tumors who achieved chemotherapy-induced amenorrhea had a significantly improved outcome (HR for amenorrhea v no amenorrhea = 0.61; 95% CI, 0.44 to 0.86; P = .004), whether or not they received tamoxifen.
CONCLUSION: Tamoxifen after adjuvant chemotherapy significantly improved treatment outcome in premenopausal patients with endocrine-responsive disease, but its use as adjuvant therapy for patients with ER-negative tumors is not recommended.
Supported in part by the Swiss Group for Clinical Cancer Research (SAKK), Frontier Science and Technology Research Foundation, The Cancer Council Australia, Australian New Zealand Breast Cancer Trials Group, National Cancer Institute Grant No. CA-75362, Swedish Cancer Society, Cancer Association of South Africa, and Foundation for Clinical Research of Eastern Switzerland.
Presented in part at the 39th Annual Meeting of the American Society of Clinical Oncology, Chicago, IL, May 31-June 3, 2003.
Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.
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