Background: Cancer subtype has recently become an increasingly important consideration when deciding the treatment strategy for breast cancer. For the estrogen receptor positive (ER+) subtype, the efficacy of adjuvant endocrine therapy is definitive, but that of adjuvant chemotherapy is controversial.
Methods: In order to evaluate the effect of adding doxorubicin (A) and cyclophosphamide (C) to tamoxifen (TAM) (ACT) on the overall survival (OS) of node-positive postmenopausal breast cancer (PMBC) patients, we conducted a randomized trial. Eligibility criteria included pathologically node-positive (n = 1-9) PMBC, stage I-IIIA disease. Patients were randomized to receive either TAM (20 mg daily) for 2 years or A (40 mg/m(2)) and C (500 mg/m(2)) plus TAM (ACT) as adjuvant therapy following surgery.
Results: One hundred twenty-nine patients were recruited (TAM 64, ACT 65) between October 1994 and July 1999. The hazard ratios for OS and relapse-free survival (RFS) were 0.58 (95 % CI 0.24-1.39; log-rank p = 0.22) and 0.45 (95 %CI 0.24-0.86; log-rank p = 0.013), respectively, in favor of ACT. The 5-year OS and RFS were 76.9 % (ER+ 87.1 %, ER- 53.3 %) and 54.9 % (ER+ 59.3 %, ER- 42.9 %) for TAM and 85.0 % (ER+ 90.0 %, ER- 77.1 %) and 76.7 % (ER+ 76.9 %, ER- 76.0 %) for ACT. A higher proportion of the patients receiving ACT than those receiving TAM experienced grade 3 decreased white blood cell count and grade 2-3 nausea.
Conclusion: The efficacy of adding AC to TAM was not high for ER+, node-positive PMBC. However, adjuvant ACT therapy was considered to be effective for ER-, node-positive PMBC.