Women who undergo radiotherapy to the conserved breast after breast-conserving cancer surgery can expect a reduction in the rate of recurrence (locoregional or distant) of approximately 50% and a reduction in the rate of death from breast cancer of about one sixth. Those are the latest findings from the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), published online in The Lancet.1
The EBCTCG report updates earlier analyses of individual patient data from randomized trials of radiotherapy after breast-conserving therapy. It adds follow-up data from nine of 10 trials analyzed earlier. It also includes information from seven new trials (six of them in low-risk women). Overall, it boosts the total number of women analyzed by almost 50%.1
The EBCTCG performed a meta-analysis using individual patient data from 10,801 women in 17 randomized trials of radiotherapy versus no radiotherapy after breast-conserving surgery. Of these women, 8,337 had pathologically confirmed lymph node status (7,287 with negative nodes and 1,050 with positive nodes).
Among the findings:
- Women randomized to radiotherapy had an average annual rate of any first recurrence 50% lower than the women who underwent surgery alone (rate ratio, 0.52; 95% confidence interval [CI], 0.48–0.56), with the greatest reduction seen in the first year after treatment (rate ratio, 0.31; 95% CI, 0.26–0.37). The reduction in the rate of recurrence persisted during years 5–9 (rate ratio, 0.59; 95% CI, 0.50–0.70).
- Women allocated to radiotherapy had a reduction in the risk of death from breast cancer of about 17% (rate ratio, 0.82; 95% CI, 0.75–0.90).
- Women who had negative nodes experienced a reduction in the average annual recurrence rate of about 50% during the first decade (rate ratio, 0.46; 95% CI, 0.41–0.51), lowering the 10-year-risk of any first recurrence from 31.0% to 15.6%, an absolute reduction of 15.4% (95% CI, 13.2–17.6; 2p<.00001).
- For women who had positive nodes, randomization to radiotherapy reduced the 1-year risk of recurrence from 26.0% to 5.1%, a fivefold reduction (rate ratio, 0.20; 95% CI, 0.14–0.29)
- Overall, one breast cancer death was avoided by year 15 for every four recurrences avoided by year 10.
“The overall findings from these trials show that radiotherapy after breast-conserving surgery not only substantially reduces the risk of recurrence but also moderately reduces the risk of death from breast cancer,” the investigators write. “These results suggest that killing microscopic tumor foci in the conserved breast with radiotherapy reduces the potential for both local recurrence and distant metastasis.”
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