Background
Individual patient data meta-analysis by the Early Breast Cancer Trialists' Collaborative Group (EBCTCG). 8,135 women from 22 randomized trials comparing RT after mastectomy (with or without ALND) vs surgery alone, or RT after BCS + ALND vs BCS + ALND alone. The key analysis focused on women with 1–3 positive nodes after mastectomy + ALND, where the survival benefit of postmastectomy RT (PMRT) had previously been uncertain.
Interventions and follow up
Arm A: RT after mastectomy or BCS
Arm B: No RT after surgery
Primary endpoint: 10-year locoregional recurrence (LRR), 20-year breast cancer mortality, and 20-year overall mortality
mFollow up: Up to 20 year
Arm B: No RT after surgery
Primary endpoint: 10-year locoregional recurrence (LRR), 20-year breast cancer mortality, and 20-year overall mortality
mFollow up: Up to 20 year
Results
Women with 1–3 positive nodes after mastectomy+ALND:
10-year LRR: 3.8% (RT) vs 20.3% (no RT), absolute reduction 16.5%
20-year breast cancer mortality: 42.3% (RT) vs 50.2% (no RT), absolute reduction 7.9% (P<.001)
20-year overall mortality: 54.7% (RT) vs 61.0% (no RT), absolute reduction 6.3% (P=.001)
Women with 0 positive nodes (pN0) after mastectomy+ALND: No significant reduction in BC mortality with RT
Women after BCS + ALND: RT reduced 10-year LRR and 20-year BC mortality (as in 2011 meta-analysis)
10-year LRR: 3.8% (RT) vs 20.3% (no RT), absolute reduction 16.5%
20-year breast cancer mortality: 42.3% (RT) vs 50.2% (no RT), absolute reduction 7.9% (P<.001)
20-year overall mortality: 54.7% (RT) vs 61.0% (no RT), absolute reduction 6.3% (P=.001)
Women with 0 positive nodes (pN0) after mastectomy+ALND: No significant reduction in BC mortality with RT
Women after BCS + ALND: RT reduced 10-year LRR and 20-year BC mortality (as in 2011 meta-analysis)
Adverse events
Main adverse events: Non-breast cancer mortality was numerically higher with RT (older techniques), partially offsetting the breast cancer mortality benefit. Net overall mortality benefit of 6.3% at 20 years remained after accounting for non-cancer deaths.
Conclusions
PMRT significantly reduces locoregional recurrence and improves 20-year breast cancer and overall survival in women with 1–3 positive nodes after mastectomy + ALND. This landmark analysis established PMRT as standard of care for the 1-3 positive node population, which had previously been a gray zone.
Key Limitations
Key Limitations: Meta-analysis of older trials with CMF-based or older systemic therapy — the proportional benefit of PMRT with modern regimens (anthracyclines, taxanes, targeted agents) may differ. RT techniques were older (higher cardiac/lung doses); modern RT reduces non-breast cancer toxicity. Patients had ALND rather than SLNB — the benefit of PMRT in patients staged with sentinel node biopsy alone is being addressed in contemporary trials (SUPREMO, TAILOR RT). These analyses cannot differentiate whether all 1-3 positive node patients benefit equally or whether risk stratification can identify low-risk patients who can safely omit PMRT.
Clinical Context
Before this 2014 meta-analysis, PMRT was generally recommended for ≥4 positive nodes but was debated for 1-3 positive nodes. This analysis definitively established benefit across all node-positive subgroups, shifting guidelines. NCCN, ESTRO, and ASTRO now recommend PMRT be discussed with or offered to patients with 1-3 positive nodes. The ongoing SUPREMO trial is evaluating if intermediate-risk patients (1-3 LN+ or high-risk N0) truly benefit in the modern systemic therapy era.
References