SWOG S0221: A phase III trial comparing chemotherapy schedules in high-risk early-stage breast cancer

George T. Budd, William E. Barlow, Halle C F Moore, Timothy J. Hobday, James A. Stewart, Claudine Isaacs, Muhammad Salim, Jonathan K. Cho, Kristine J. Rinn, Kathy S. Albain, Helen K Chew, Gary V. Burton, Timothy D. Moore, Gordan Srkalovic, Bradley A. McGregor, Lawrence E. Flaherty, Robert B. Livingston, Danika L. Lew, Julie R. Gralow, Gabriel N. Hortobagyi

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


Purpose: To determine the optimal dose and schedule of anthracycline and taxane administration as adjuvant therapy for early-stage breast cancer. Patients and Methods: A 2 × 2 factorial design was used to test two hypotheses: (1) that a novel continuous schedule of doxorubicin-cyclophosphamide was superior to six cycles of doxorubicin-cyclophosphamide once every 2 weeks and (2) that paclitaxel once per week was superior to six cycles of paclitaxel once every 2 weeks in patients with node-positive or high-risk node-negative early-stage breast cancer. With 3,250 patients, a disease-free survival (DFS) hazard ratio of 0.82 for each randomization could be detected with 90% power with two-sided α =.05 Overall survival (OS) was a secondary outcome Results Interim analyses crossed the futility boundaries for demonstrating superiority of both once-per-week regimens and once-every-2-weeks regimens. After a median follow-up of 6 years, a significant interaction developed between the two randomization factors (DFS P =.024; OS P = 010) in the 2,716 patients randomly assigned in the original design, which precluded interpretation of the two factors separately. Comparing all four arms showed a significant difference in OS (P = 040) but not in DFS (P =.11), with all treatments given once every 2 weeks associated with the highest OS. This difference in OS seemed confined to patients with hormone receptor-negative/human epidermal growth factor receptor 2 (HER2) -negative tumors (P =.067), with no differences seen with hormone receptor-positive/HER2-negative (P =.90) or HER2-positive tumors (P =.40) Conclusion: Patients achieved a similar DFS with any of these regimens. Subset analysis suggests the hypothesis that once-every-2-weeks dosing may be best for patients with hormone receptor-negative/HER2-negative tumors.

Original languageEnglish (US)
Pages (from-to)58-64
Number of pages7
JournalJournal of Clinical Oncology
Issue number1
StatePublished - Jan 1 2015

ASJC Scopus subject areas

  • Cancer Research
  • Oncology


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