The primary aim of National Surgical Adjuvant Breast and Bowel Project (NSABP) B-28 was to determine whether four cycles of adjuvant paclitaxel (PTX) after four cycles of adjuvant doxorubicin/cyclophosphamide (AC) will prolong disease-free survival (DFS) and overall survival (OS) compared with four cycles of AC alone in patients with resected operable breast cancer and histologically positive axillary nodes.

Between August 1995 and May 1998, 3,060 patients were randomly assigned (AC, 1,529; AC followed by PTX [AC --> PTX], 1,531). Patients > or = 50 years and those younger than 50 years with estrogen receptor (ER) or progesterone receptor (PR) -positive tumors also received tamoxifen for 5 years, starting with the first dose of AC. Postlumpectomy radiotherapy was mandated. Postmastectomy or regional radiotherapy was prohibited. Median follow-up is 64.6 months.

The addition of PTX to AC significantly reduced the hazard for DFS event by 17% (relative risk [RR], 0.83; 95% CI, 0.72 to 0.95; P = .006). Five-year DFS was 76% +/- 2% for patients randomly assigned to AC --> PTX compared with 72% +/- 2% for those randomly assigned to AC. Improvement in OS was small and not statistically significant (RR, 0.93; 95% CI, 0.78 to 1.12; P = .46). Five-year OS was 85% +/- 2% for both groups. Subset analysis of the effect of paclitaxel according to hormone receptors or tamoxifen administration did not reveal statistically significant interaction (for DFS, P = .30 and P = .44, respectively). Toxicity with the AC --> PTX regimen was acceptable for the adjuvant setting.

The addition of PTX to AC resulted in significant improvement in DFS but no significant improvement in OS with acceptable toxicity. No significant interaction between treatment effect and receptor status or tamoxifen administration was observed.