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Breast Cancer · Surgical · Early breast cancer

NSABP B-06

Can breast-conserving surgery provide survival comparable to mastectomy, and does whole-breast irradiation reduce ipsilateral recurrence after lumpectomy?

PopulationWomen with stage I–II invasive breast cancer, tumour ≤4 cm, clinically negative or positive axillary nodes.RandomizationTotal mastectomy vs lumpectomy alone vs lumpectomy + whole-breast irradiation, with axillary dissection.Sample2,105 randomized; long-term analyses included 1,851 eligible patients with known nodal status.Primary clinical issueLocal control versus extent of surgery, with survival as the key oncologic endpoint.

Absolute Effect

Local recurrence
20-year IBTR: 39.2% lumpectomy alone vs 14.3% lumpectomy + RT

Absolute reduction ≈24.9 percentage points with irradiation. At 12 years, cumulative ipsilateral recurrence was 35% vs 10%.

Survival
No significant OS difference

Long-term follow-up found no significant difference in overall, disease-free or distant disease-free survival between mastectomy and breast-conserving approaches.

Clinical interpretation

The trial separated two questions: lumpectomy can achieve survival outcomes comparable to mastectomy in appropriately selected early breast cancer, while radiotherapy substantially reduces ipsilateral breast recurrence after lumpectomy.

The absolute local-control benefit of RT is large, whereas the survival endpoint was not improved by choosing mastectomy over breast conservation.

Treatment burden, toxicity and limitations

Breast conservation requires postoperative RT in the trial strategy, while mastectomy avoids breast irradiation. The trial used historical surgery, systemic therapy and radiation techniques, so absolute recurrence risks should not be transplanted directly to contemporary patients.

A major historical data-integrity concern involving one participating centre prompted an NCI audit; the audit supported the adequacy of the reanalysed endpoint data.

NNT / NNH

NNT for preventing one ipsilateral recurrence can be approximated as 1/0.249 ≈ 4 over 20 years for lumpectomy + RT versus lumpectomy alone, but this is a long-horizon recurrence NNT rather than an NNT for survival.

NNH is not calculated because the pivotal reports do not provide a clean fixed-time serious-toxicity comparison suitable for a defensible NNH.

Primary / authoritative sources

NSABP B-06 12-year reanalysis — PubMed

NSABP B-06 20-year follow-up — PubMed

NCI audit of B-06 — PubMed

Current-practice context · reviewed 14 October 2026

NSABP B-06 established breast-conserving surgery with radiotherapy as an effective alternative to mastectomy for appropriately selected early breast cancer, with comparable long-term survival. The trial's local-control results remain foundational; modern selection also depends on tumour extent, margins, genetic risk, radiotherapy feasibility, systemic therapy and patient preference.

Current guideline guidance ↗