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Breast Cancer · Endocrine Therapy · Adjuvant

NSABP B-14

In ER-positive, node-negative breast cancer, does 5 years of tamoxifen improve outcomes compared with placebo?

PopulationAbout 2,844 women with ER-positive, node-negative breast cancer.InterventionTamoxifen 10 mg twice daily for 5 years.ComparatorPlacebo.Primary clinical outcomeDisease-free survival.

Absolute Effect

At 5 years, DFS was 82% with tamoxifen vs 72% with placebo: an absolute improvement of 10 percentage points, corresponding to an NNT of approximately 10.

Long-term follow-up confirmed durable benefit from the original 5-year tamoxifen strategy. Extending tamoxifen beyond 5 years in the B-14 rerandomization did not add benefit.

Clinical interpretation

B-14 was foundational evidence for adjuvant endocrine therapy in ER-positive node-negative breast cancer. The absolute benefit is recurrence reduction rather than a demonstrated large early overall-survival gain.

Duration question

Among women disease-free after 5 years of tamoxifen, continuing tamoxifen rather than stopping did not improve DFS or survival in the subsequent randomized comparison.

Sources

NSABP updated findings · Long-term duration analysis

Current-practice context · reviewed 14 October 2026

NSABP B-14 established tamoxifen benefit in ER-positive node-negative breast cancer. Endocrine therapy remains fundamental, but current selection includes menopausal status, aromatase inhibitors, extended duration for higher-risk disease, tolerability and genomic-risk tools; the trial does not determine the optimal modern duration for every patient.

Current guideline guidance ↗