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Breast Cancer · Medical · Neoadjuvant therapy

NSABP B-18

In operable breast cancer, does giving doxorubicin/cyclophosphamide before surgery improve survival compared with giving the same chemotherapy after surgery?

Population1,523 eligible women with operable breast cancer.InterventionFour cycles of preoperative doxorubicin/cyclophosphamide.ComparatorThe same four cycles after surgery.Key endpointsOS, DFS, tumour response and breast-conservation rate.

Absolute Effect

9-year OS
69% vs 70%

Preoperative versus postoperative AC; P=.80.

9-year DFS
55% vs 53%

No statistically significant difference; P=.50.

Surgical effect

Preoperative chemotherapy reduced tumour size in 80% of patients and produced more breast-conserving surgery, particularly among women with larger tumours.

Clinical interpretation

B-18 supports neoadjuvant therapy as a strategy for downstaging and surgical planning rather than as a survival-improving change in chemotherapy timing.

The trial also showed that response to preoperative chemotherapy carries prognostic information, a concept that became central to modern subtype-specific neoadjuvant therapy.

NNT / NNH

No NNT is calculated for OS or DFS because there was no demonstrated survival advantage. The absolute surgical benefit depends on baseline tumour size and operability.

Limitations

The chemotherapy regimen and systemic therapy landscape predate modern HER2-directed and subtype-specific treatment.

Primary / authoritative sources

NSABP B-18 9-year results — PubMed

Local-regional response report — PubMed

Current-practice context · reviewed 14 October 2026

NSABP B-18 established that preoperative AC can increase breast-conservation opportunities compared with postoperative AC without a survival advantage from timing alone. Neoadjuvant therapy is now selected by subtype and stage—especially for TNBC and HER2-positive disease where response guides post-neoadjuvant treatment—rather than used routinely for every operable breast cancer.

Current guideline guidance ↗