Effect of radiotherapy after breast-conserving surgery on 10-year recurrence and 15-year breast cancer death: meta-analysis of individual patient data for 10,801 women in 17 randomised trials.
Level 1 - systematic review of randomized trials
Individual patient data meta-analysis of randomized controlled trials
PubMed 22019144 · doi:10.1016/S0140-6736(11)61629-2
What was done
An individual patient data meta-analysis of 10,801 women across 17 randomised clinical trials evaluated radiotherapy versus no radiotherapy following breast-conserving surgery. Pathological nodal status was confirmed in 8,337 patients (7,287 node-negative [pN0] and 1,050 node-positive [pN+]). Outcomes evaluated were 10-year risk of any first recurrence (locoregional or distant) and 15-year risk of breast cancer death, stratified by baseline prognostic factors (age, tumor grade, estrogen receptor status, tamoxifen use, extent of surgery).
What was found
Overall, radiotherapy reduced the 10-year risk of any recurrence from 35.0% to 19.3% (absolute reduction 15.7%, 95% CI 13.7–17.7, p<0.00001) and 15-year breast cancer mortality from 25.2% to 21.4% (absolute reduction 3.8%, 95% CI 1.6–6.0, p=0.00005). - In pN0 disease (n=7,287): 10-year recurrence fell from 31.0% to 15.6% (absolute reduction 15.4%, 95% CI 13.2–17.6, p<0.00001) and 15-year mortality from 20.5% to 17.2% (absolute reduction 3.3%, 95% CI 0.8–5.8, p=0.005). When categorized by predicted 10-year recurrence reduction (large ≥20%, intermediate 10–19%, lower <10%), absolute 15-year mortality reductions were 7.8% (95% CI 3.1–12.5), 1.1% (95% CI -2.0 to 4.2), and 0.1% (95% CI -7.5 to 7.7), respectively (trend p=0.03). - In pN+ disease (n=1,050): 10-year recurrence fell from 63.7% to 42.5% (absolute reduction 21.2%, 95% CI 14.5–27.9, p<0.00001) and 15-year mortality from 51.3% to 42.8% (absolute reduction 8.5%, 95% CI 1.8–15.2, p=0.01). Overall, approximately one breast cancer death was avoided by year 15 for every four recurrences avoided by year 10.
Why it matters
This analysis confirms that local recurrence prevention from radiotherapy translates directly into a long-term breast cancer survival benefit, with absolute gains tightly linked to an individual's baseline recurrence risk.
Limits
The included trials reflect historic cohorts whose systemic treatments, surgical margin definitions, and radiotherapy delivery techniques may differ from modern standards. Node-positive representation was relatively small (n=1,050) compared to node-negative disease, and the abstract does not report non-breast-cancer mortality or long-term radiation toxicity.
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